GC23A-1323
NASA NEESPI Data Center pdf version of the poster
The Northern Eurasia Earth Science Partnership Initiative (NEESPI) is an international program of coordinated research on the state and dynamics of ecosystems in Northern Eurasia and their interactions with the Earth's Climate system. The program is designed to enhance scientific knowledge of these ecosystems as well as to develop predictive capabilities to support informed decision-making and practical applications. The NASA NEESPI Data Center is a multi-sensor, online, easy access data archive and distribution system to provide advanced data management capabilities in support of the NEESPI scientific objectives. Its tools include data analysis and visualization, and other techniques for better science data usage. The NASA NEESPI Data Center portal integrates remote sensing data from MODIS, AIRS, OMI, and other instruments on board polar-orbiting satellites, along with customized data products from climatology data sets and models into a single one-stop- shopping interdisciplinary NASA-NEESPI data center. The presentation will provide status and the most recent achievements of the NASA NEESPI Data Center. In the recent months, the emphasis has been put on analyzing and then preparing steps for the online data analysis by bringing data to common grids while preserving available and statistically important information from the higher resolution inputs. The NESSPI instance of Giovanni, the popular online visualization and analysis tool, features the first batch of atmospheric, fire and snow data products, organized to provide quick and user-friendly exploration means.
http://neespi.gsfc.nasa.gov/
GC23A-1324
NEESPI Science and Data Support Center for Hydrometeorological Information in Obninsk, Russia pdf version of the poster
Reflecting the long history of ecological and geophysical research in the region, there are numerous archival geophysical datasets that have been collected for routine monitoring or for special studies. In many cases, these data have little distribution or visibility outside of the host country or institution. One of the priorities of NEESPI is to identify these datasets and promote their distribution to address the science goals of the NEESP Initiative. During the NEESPI implementation, different types of in-situ information will be used: hydrometeorological, socio- economic, land-cover, and land-use data. Each type of these data has their peculiarity in collection, archiving, and pre-processing. For example, the system of hydrometeorological observations within the former Russian Empire and USSR has been gradually developed during the past 200 years. The number of major synoptic stations over Russia and the former USSR varied from ~100 in the past decade of the 19th century to maximum of ~ 3500 in 1985. At that time, however, precipitation was measured at ~11,000 locations. Presently, in Russia there are ~1900 synoptic stations. Description of data holdings and their management at the NEESPI Science and Data Support Center for Hydrometeorological Information in Obninsk, Russia will be presented at the Meeting.
GC23A-1325
Climate Variations and Changes in the Frequency of Climate Extreme Events in Russia pdf version of the poster
Daily temperature (mean, minimum and maximum), wind speed, and atmospheric precipitation data from 940 stations were used to analyze variations in the space-time distribution of extreme temperatures, precipitation and wind across Russia during the past six decades. The seasonal numbers of days, when daily air temperatures (wind, precipitation) were higher or lower than selected thresholds, were used as indices of climatic extremes. All values falling within the intervals ranged from the lowest percentile to the 5$^{th}$ percentile and from the 95$^{th}$ percentile to the highest percentile for each month within each season were considered as daily extremes. The numbers of days with these extremes, N, were determined for each season of each year. Thereafter, linear trends in N were calculated for each station for the time period of interest. The number of winter (DJF) days with maximum temperatures higher than the 95$^{th}$ percentile has increased over most of Russia. The largest linear trends were observed in the centers of the European part of Russia and Siberia. Using high-quality daily and 3-hourly precipitation data sets, the changes in the number of days with different sums of precipitation were assessed. A tendency of increase in the number of days with heavy precipitation was observed throughout the nation, especially during the last 30-year period.
GC23A-1326
Typhoon Strength, Related Precipitation, and Sea Surface Temperatures in the Southeastern Part of the NEESPI domain
Model simulations using CO$_{2}$-induced sea surface temperature increases indicate that TC wind speeds and related daily precipitation may increase. We investigated changes in the TC-related rainfall distributions as a function of TC strength at landfall and impact of SST ahead of TCs on the TC strength for several preferred tropical cyclone regions. Our findings were that a warmer climate and (projected with it) SST increases over the tropical North Atlantic and Pacific Oceans will likely be accompanied by more frequent strong landfalling hurricanes over the U.S. and China coasts. The fraction of strong hurricanes that make landfall on these coasts is positively correlated with daily SSTs in the path of the TCs. But, there were no landfalling strong hurricanes at, or above Category 3 in the Saffir-Simpson Hurricane Scale (strong to catastrophic hurricanes) when the SST was below the threshold of $28\deg$C, which is likely a primary reason of their absence at the Russian Far East coast during the past fifty years. However, during the past 20 years there have already been strong landfalling typhoons north of Shanghai (with SST = $28.9\deg$C) and several tropical storms that hit China north of $40\deg$N and/or Russia with SST ahead of the storm tracks well above $28.5\deg$C. With the ongoing warming (including the SST increases in the western part of the Northern Pacific by $0.8\deg$C 100yr$^{-1}$ during the typhoon season) these situations may become more frequent. Therefore, we focus on the southeastern edge of the NEESPI region (Russian Far East, northern China, Korea, and northern Japan) to assess the relationships that control the TC activity changes with the SST increase and to trace the above mentioned threshold shift northward during the typhoon season.
GC23A-1327
Response of River Runoff in Cryolithic Zone of Eastern Siberia (Lena River Basin) to Recent and Future Climate Warming
During several last decades significant climate warming is observed in permafrost regions of Eastern Siberia. These changes include rise of air temperature as well as precipitation. Changes in regional climate are accompanied with�river runoff changes. Seasonal and long-term changes of river runoff in different parts of the Lena river basin are characterized by significant differences. The main causes of these differences are regional distinctions of climatic conditions, types and properties of permafrost, character of relief, hydrogeological conditions, features of surface and underground water interaction, types and properties of vegetation and soil covers and also regional features of cryogenic processes and phenomena. The above mentioned causes determine non-uniform long-term (since 1930th) response of river runoff changes (its annual amount and its distribution on seasons and role of genetic components) to recent climate changes within the Lena river basin. Nevertheless results of analysis of river runoff long-term trends in different parts of the Lena river basin show that over the past 10-15 years rather synchronous river runoff increase is observed. But scales of the mentioned increase are different in different parts of this one of the largest river basins of the World. According to the results of hydrological modeling the expected anthropogenic climate warming in XXI century can bring more significant river runoff increase in the Lena river basin as compared with the recent one. The hydrology-related consequences of climate warming have been evaluated for the plain part of the Lena river basin basing on a macroscale hydrological model featuring simplified description of processes [Georgiadi, Milyukova, 2000, 2002, 2006]. �
GC23A-1328
Northern Eurasian Wetlands and the Carbon Cycle: Model Estimates of Carbon Storage and Methane Emissions
The Eurasian Arctic drainage constitutes over ten percent of the global land area, and stores a substantial fraction of the terrestrial carbon pool in its soils and boreal forests. Specifically, boreal forests in this region constitute an estimated carbon sink of 0.5 Pg/y. However, assessments of carbon storage and fluxes in this region, and their role in climate change, vary considerably due to large uncertainties in the extent of wetlands, which both store carbon as peat and emit carbon as methane. Accurate estimates of wetland extent have been confounded by insufficient resolution of satellite imagery and poor coverage of in situ observations. In this study we refine these estimates of wetland extent, carbon storage, and methane emissions using a system of linked large-scale models of hydrology, terrestrial carbon dynamics, and methane emissions. Large-scale hydrology comes from the Variable Infiltration Capacity (VIC) hydrological model, which includes an updated lake/wetland parameterization that estimates the water table depth as a function of both lake level and wetland soil moisture. Fast ecosystem processes such as photosynthesis and respiration are simulated via the Biosphere Energy- Transfer Hydrology (BETHY) terrestrial carbon model. Methane emissions in areas of open water or saturated soil are simulated with the Walter-Heimann methane model. We validate this modeling system with respect to in situ observations of soil moisture and temperature, evaporation, and fluxes of CO2 and methane at flux towers at Fyodorovskoje, Hakasia, and Cherskii, Russia, over the period 1998-2004. Sensitivity to calibration parameters such as the rooting depth and the proportionality between methane production rate and NPP are also explored.
GC23A-1329
Simulation of northern Eurasian wetland dynamics using the Variable Infiltration Capacity Model
Lakes and wetlands are particularly prevalent in large regions of the Arctic, where the presence of permafrost and modest relief impedes the subsurface drainage of water. Current wetland areas are in transition as a result of pressure from global environmental changes, such as climate, with implications for the regional water and carbon balance. The variable infiltration capacity (VIC) macro scale hydrological model is used to assess the sensitivity to climate of wetland extent and corresponding hydrologic fluxes. The effect of lake and wetlands are currently represented in the VIC model through an additional wetland land surface class which does not relate upland soil moisture to the variations in lake level. This work describes a series of improvements to better integrate moisture exchanges within the VIC lakes and wetland algorithm, including relating the variable lake fraction to the soil saturated fraction predicted by the VIC runoff curve and computing the effective water table depth and hydraulic gradient for exchange of subsurface moisture with the grid cell lake. The updated VIC lake model will be evaluated in comparison to satellite observations of wetland extent in European Russia and in situ observations of monthly water table depth, soil moisture, evaporation, and runoff obtained over a period of three decades (1960-1990) from the Valdai water-balance research station located south of St. Petersburg, ($57.6\deg$N, $33.1\deg$E) in the forest zone of Russia. This work was carried out at Purdue University, and at the Jet Propulsion Laboratory, California Institute of Technology and the University of Washington, under contract to the National Aeronautics and Space Administration
GC23A-1330
Wetland Expansion on the Southern Edge of the West Siberian Sphagnum Wetlands pdf version of the poster
The southern border of Vasyugan wetland was chosen to analyse the long term trend in organic carbon (peat) accumulation and wetland expansion processes. In our study, the comprehensive field (soil/peat and geobotanical) studies were conducted and the results were extrapolated using Landsat ETM+ satellite images. Two types of interaction (ecotones) between forest and wetland were revealed within the study area. Variations in the trend of peat accumulation were found in two types of ecotones, strongly affected by topography and chemical properties of the mineral subsoil of wetland basin. One ecotone is represented by a range of forest ecosystems on flat terrain, and differs from another by the absence of reed communities. Flat topography, coupled with loamy structure and poorness of the subsoil provide conditions for the �permanent� formation of wetlands in the forest ecotone. Progression of the Sphagnum wetlands toward the adjoining deciduous forests was confirmed by existence of the residual soils, recently covered by peat sediments. Another, forest-reeds ecotone is situated on the more uneven terrain providing the path for water flow from the periphery of wetland basin. This causes the recurrence of drying and wetting of upper peat layers, resulting in the fluctuation in the carbon-storage capability of the area and recurring peat degradation on the periphery of peatland basin. The reed ecosystems are the sure indicator of carbonates located close to the land surface. The high concentration of carbonates in subsoil inhibits the advance of Sphagnum mosses and subsequent expansion of wetlands (i.e. �intermittent� wetland formation). Finally, the forest�wetland boundary areas on the satellite images were classified into different types of ecotones described earlier. The final layout, prepared in the scale of 1:200K, demonstrates the evident activity of the wetland expansion processes even in the relatively dry climate without excess of precipitation over evaporation. The ratio between areas with permanent and intermittent types of wetland expansion was estimated as 3:1.
GC23A-1331
Simulation and forecast of the Tien Shan glacier's changes
Two mathematical models: glacial-covered areas/glacier numbers and glacial volume changes developed based on assessment of the glacier recession that occurred in a Tien Shan glacial massif for the last 60 years. According to estimations performed in the Akshiirak glacierized massif for the period from 1943 to 1977, change in mean altitude (Hm) of each individual glacier in the massif is a linear function of the change in the mean of Equilibrium Line Altitude (ELA). For the Aksiirak massif, the ratio between Hm and ELA is 1/4. For other Tien Shan glacier basins the ratios, determined from topographic data and NASA ESE System products vary from 1/3 to 1/5. The ELA under air temperature and precipitation changes was calculated to estimate the changes in mean ELA and area of each individual glacier. In a stepwise approximation, we took into account two new small glaciers that appeared as a result of the disintegration of a larger glacier. The simulation of the glacier-covered areas and volumes changes are based on two output/prediction models. The first model focuses on the forecast of glacier characteristics using an iteration technique and based partly on overlap domains with areas of about 1000 km2. The ELAs were subsequently increased by 1 m to calculate a new adjusted glacier surface area in each domain. For the second model, all calculations for the glaciers were completed through a differential calculus iteration technique with 1m of ELA increase. Hypothetical Tien Shan climate-change scenarios imposed as a stepwise progression predict that by the year 2100, the ELA could rise up to 407 m due to an average increase in air temperature of 3�� and an average increase in precipitation of 1.2 times the current level in Tien Shan. The number of glaciers, glacier covered areas and glacier volumes are predicted to be 77.6 percent from the current state. The threshold conditions of glacier distribution and disappearance (when Hm < ELA) under air temperature and precipitation changes were also estimated.
http://www.sci.uidaho.edu/cae/index.html
GC23A-1332
Reconstruction of a 50-Year Record of Seasonal Snow Cover in Central Asia
Water resources in the mountains of interior Eurasia are highly vulnerable to climate change because the closed drainage basins are very sensitive to the changes in energy and mass fluxes at the land surface and, as a result, the near-surface physical conditions such as snow cover which affect river. Current and further expected declines in the water resources of the central Asian mountains are related to factors such as degradation of glaciers and seasonal snow cover extent, the changes in precipitation partitioning among land surface stores, and evaporation fluxes. To study snow cover impact on river runoff formation in the Tien Shan mountains of central Asia for the last half a century, we have applied to a combination of remote sensing, in situ snow course, and meteorological data. Here we present preliminary results of comparing AVHRR-derived Snow Covered Area (SCA) with the ground data over selected Tien Shan representative basins for the period of overlap between in situ and remote observations from 1979 to 1991. For the runoff modeling purposes maximum SCA was determined for each year at the dates of maximum snow accumulation determined by snow surveys data in the studied basins. From 1991 to present the maximum SCAs were determined independently from AVHRR and MODIS data and validated with Landsat data. The MODIS fractional snow cover product for the 5 seasons (2000/01 through 02005/06) characterized the spatial and temporal patterns of snow cover in each studied basin which we relate to the surface observational data (air temperature, and larger scale synoptic patterns revealed in the Numerical Weather Prediction (NWP) products. This SCA pattern analysis is applied to in situ snow course, and meteorological data for the period 1950 to 1979 to estimate maximum SCA for runoff modeling.
GC23A-1333
Glacier Area and River Runoff Changes in the Head of Ob River Basins During the Last 50 Years
The Altai mountains in Siberia define southern periphery of the Asian Arctic Basin, and the Ob River is a major Siberian river fed by fresh water from Altai glaciers. Intensification of glacier melt in the head of Ob River since the middle of 20th century may have a considerable influence on the water resources and hydrological regime of Siberian rivers, and freshwater budget of the Arctic Ocean. In our research we estimated glacier area and runoff changes in the Aktru River basin (34.9 km$^{2}$, 45% covered by glaciers) in the Central Altai using remote sensing data and in situ glaciological and hydrological observations. The measurements of the glacier mass-balance started in this basin in 1952 as a part of the World Glacier Monitoring Service, however an accurate estimation of the glacier area change in the last two decades have not been accomplished. In our research we used aerial photographs (1952, 1975), Corona (1968) and ASTER (2004) images, and Ground Control Points collected with DGPS in 2005 and 2006 field surveys. Preliminary analysis shows that area of the studied glaciers reduced up to 7% and glacier tongues retreated up to 600 m from 1952 to 2004. The rate of the glacier recession doubled between 1975 and 2004 and the river runoff increased by 30 mm/year at the head of Ob river tributaries fed by snow and glacier melt water. During the period from 1954 to 2004 annual (mainly summer) air temperature increased by 0.1 C$\deg$ a decade and precipitation (mainly spring and summer) increased by 50 mm at an elevation of 2000 m.
GC23A-1334
Development of a Regional Dust Modeling System for Central and East Asia Under the NEESPI Initiative
The Northern Eurasia Earth Science Partnership Initiative, NEESPI, is a multi-disciplinary, international program aimed to develop a comprehensive understanding of the Northern Eurasian terrestrial ecosystem dynamics, biogeochemical cycles, surface energy and water cycles, and human activities. Both land-cover and land-use changes, and perturbed atmospheric composition (including atmospheric dust burdens) have been well recognized as the key climate forcing agents, though quantification of their impacts on the climate system has been proven difficult. Up to date, assessments of the magnitude of the impacts of each of these agents remain highly uncertain. To improve the modeling capability of the prediction of dust impacts on the climate and environment, we have been developing a regional dust modeling system by incorporating the dust module DuMo into the NCAR Weather Research and Forecasting (WRF) model. Currently, the DuMo includes several formulations of the so called simple dust emission scheme in which the erodible fraction and threshold friction velocity are prescribed (Darmenova and Sokolik, 2006). This presentation will report on the implementation and testing of two state-of-art dust emission schemes originally developed by Marticorena and Bergametti (1995) (and recently applied by Laurent et al. (2006) to East Asia) and Shao (2001, 2004). We examine the similarities and differences between physical parameterizations of the dust emission process in these schemes as well as address the availability of required input data for Central and East Asia. By incorporating these schemes in the DuMo, we perform simulations of representative dust storm events in the springs of 2001, 2003, and 2004 to delineate the relative role of meteorological and land parameters in the dust emission in Central and East Asia, addressing regional specifics. Intercomparison of the regional dust modeling systems (WRF/DuMo vs. RAMS/CFORS (developed by Uno et al.)) is also being performed to bracket the model-dependent uncertainties in simulated dust fluxes. The results will be presented and discussed with the focus on establishing a methodology for determining the �best� value and dispersion of size-resolved dust fluxes simulated with the WRF/DuMo regional modeling system.
GC23A-1335
Reconstruction of a 50-year climatology of dust storms in Central and East Asia from ground- based and satellite observations
In support of the Northern Eurasia Earth Science Partnership Initiative (NEESPI), we have been working on the development of the Asian Dust Databank by integrating the diverse satellite and ground-based data on land- use/land-cover, atmospheric mineral dust, and climatic variables in Central and East Asia. The ultimate goal of this effort is to gain a better understanding of interactions between land-cover and land-use changes and varying atmospheric dust burden and their roles in and linkages to climate changes which have been observed in Northern Eurasia over the past 50 years. This paper will present our work towards establishing an observation-based climatology of dust storm events, which is one of the key components of the Asian Dust Databank. An integrated analysis of satellite and ground- based visibility observations will be presented with the goal to reconstruct the timing, duration, and area coverage of dust outbreaks on a case-by-case basis. Satellite multi-sensor observations used in this study include TOMS (Total Ozone Mapping Spectrometer), and MODIS (Moderate-Resolution Imaging Spectroradiometer) aboard the Terra and Aqua satellites. Several other satellite sensors will be included in the near future. In addition to visibility data reported from the weather stations, we have been compiling the historical data on dust storm occurrences from monitoring stations as well as data from the field expeditions conducted over the years in the region of interest. Midrange transport of Asian dust will be also documented and included in the database. Given various intrinsic limitations of individual data sets, an integrated analysis methodology is being developed to provide a reliable climatology.
GC23A-1336
Application of a PC analysis of remote sensing spectral reflectance data to determine source regions for dust storms.
The source regions of deserts over which dust is lifted into the air occur on relatively small scales and hve been difficult to characterize geographically. The research programs supporting NASA's terra and aqua satellites have pioneered the development of quality controlled climatologies of surface information, that should include features characteristic of dust source regions. With quality satellite data, patterns can be distinguished that are likely to indicate real geophysical features. Zhou et al. (2005) applied a principle component (PC) analysis to the North African desert that revealed intriguing spatial structures. It represents the spatial patterns with a limited number of PC's that maximize the covariances between spectral bands averaged over space. Such analysis acts as a filter of nonphysical information and should highlight commonly occurring small scale features, some of which are likely connected to dust source regions. We present a new such analysis for the Taklamakan desert of China. The first 2 or 3 modes are removed as being of too coarse a spatial scale to represent source regions. Features of the remaining 3 or 4 patterns of significant amplitude are examined for their possible relevancy to dust uplifting. In particular, patterns that show seasonality of vegetation are deemed unlikely to be so relevant. Distinctions in the spectral patterns and MODIS BRDF kernels of remaining terms are examined for their likely indication of a dust source region.
GC23A-1337
Effects of air pollution, drought, and land use on net primary productivity and carbon storage in Northern China
Terrestrial ecosystems in Northern China have experienced multiple environmental stresses including air pollution, drought and land use. Since the early 1980s, the unprecedented combination of economic and population growth has led to a dramatic land transformation and severe air pollution across large portion of China. China's emissions of ozone precursors are expected to be doubled in the next 20 years. Evidence indicates that more than 90% terrestrial plants can be affected by ozone pollution. However, little is known about how elevated tropospheric ozone concentration interacted with drought and land use has influenced net primary productivity and carbon storage in the terrestrial ecosystems of China. In this study, we have used newly developed Dynamic Land Ecosystem Model in conjunction with spatially-explicit historical data sets of ozone, carbon dioxide, climate and land use to assess to what extent ozone pollution combining with other environmental factors has influenced net primary productivity and carbon storage in Northern China for the period from 1961 to 2000.
GC23A-1338
Coupled climate and human impacts on the wetland ecosystem in Zhalong Nature Reserve of Northeastern China
The 840-squaure-mile (2,175-km2) Zhalong Nature Reserve is located in the northern Heilongjiang Province of China. Known for its migratory red-crowned cranes, the reserve was listed in the World Important Wetlands in 1992 by the United Nations. However, in recent years, Zhalong's wetlands have been facing increasingly threats from both intensified human exploitation and recent climate change. Using meteorological observations over the past 50 years, remote sensing images over the past 30 years, field surveys, and geospatial technologies, we conducted an analysis to improve our understanding of the dynamics of wetlands as a function of socioeconomic and climatic forcing. Specifically, we attempted to address the following coupled issues and questions: 1) how have the climate and socioeconomics in recent years changed in Zhalong Nature Reserve and 2) what are the ecological consequences of increasing human activities and changes in policies coupled with climate change? The analysis of the climate pattern and human activities suggest that the policy changes played a major role in land use/cover change and imposed a significant impact on the wetland ecosystem dynamics. The human activities appear to be the dominant factor in driving recent changes in wetland ecosystems while the climate change appears to have a secondary role affecting wetland ecosystems.
GC23A-1339
Effects of land use change on water use fluxes in the semi arid region of Inner Mongolia pdf version of the poster
Land Use/Cover in Inner Mongolia, a semi-arid region that is predominantly steppe in Northern Eurasia has undergone significant changes resulting in inter-annual climatic anomalies as well as changes in the local hydrological cycle and energy balance. A comparison of MODIS derived IGBP Land cover with the AVHRR derived IGBP (1992-93) land cover product showed that the proportion of grassland, agricultural, & barren land cover/use increased with a subsequent decrease in shrub lands and forests. A suite of MODIS derived biophysical variables such as EVI, GPP, as well as water content indices such as LSWI and NDSVI were studied in context of LULC types to study the effects of land cover change (categorical) as well as degraded grassland and desert steppe (fractional cover change). The MODIS derived water content indices were validated by spectro-radiometer readings, obtained during a ground truthing campaign. Initial results from the 2005 growing season suggest that croplands exhibit more water use than grasslands, the dominant land cover type.
GC23A-1340
Lake Sediment Records of Holocene Climate Change in the Khanuy Valley, Arkhangai Aimag, North-Central Mongolia
Late Holocene geochemical records from three lakes in the Khanuy Valley, Arkhangai Aimag, north-central Mongolia document centennial and millennial-scale climate variability within central Asia. The oldest sediments of the shallow Tsegeen Nuur basin ($49.09\deg$N, $101.86\deg$E) and nearby Sharga Nuur ($48.92\deg$N, $101.96\deg$E) indicate lake filling and open water deposition by at least 3600 years before present (yrs. B.P.). Minimum oxygen isotope (\delta$^{18}$O) values, suggesting high water levels and relatively wet conditions, are preserved in biogenic carbonates (ostracod shells) from both lakes during the same time interval. Mid-core sedimentary sequences in Tsegeen Nuur and Sharga Nuur ( ~1900 to 600 yrs. B.P.) exhibit weak blocky and columnar structures. These lithologic changes indicate lake drying, sub-aerial exposure, and some soil development. However, these soil-like horizons contain sparse shell remains of both ostracods and bivalves and therefore suggest that both lakes held water at least periodically during this time. Ostracod shells from this interval record the greatest \delta$^{18}$O values and support the inference for a low lake stage. No evidence exists for lake desiccation at a deeper and higher elevation lake core site (Doroo Tsagaan Nuur, $49.022\deg$N, $101.201\deg$E) located approximately eighty kilometers west of the Tsegeen and Sharga Nuur basins. This also suggests that although late Holocene moisture availability was significantly reduced, aridification was likely not extreme. At Tsegeen and Sharga Nuur, wet conditions appear to have returned after 600 yrs. B.P., as indicated by a decrease in \delta$^{18}$O values and the resumption of lacustrine deposition. It should be noted that archaeological evidence suggests that the Khanuy Valley was greatly populated between ~3200 and 2700 yrs. B.P. (Allard 2006) roughly coinciding with the wettest period recorded within these lake core sites. Human occupation of the Khanuy Valley may therefore have been linked, at least in part, to regional climate changes.
GC23A-1341
Estimates of hydrometeorological risks and distribution functions for the intensity of atmospheric vortices from reanalysis and model simulations
The data from NCEP/NCAR reanalysis provide a basis for defining new statistical features of atmospheric general circulation and determining their variations during the time of the climate change. Here we describe the distribution functions for the weather-forming atmospheric vortices, cyclones and anticyclones, within the latitudinal belt 20-800N for the time span from 1952-2000. We use the geopotential heights at the isobaric surface 1000 hPa and determine a vortex as an area within the outermost closed isohypse. The number of cyclones per year practically did not change during analyzed 49 years, however, their seasonal distributions do change: the cyclone frequency increased in the warmer half-year by about 2%, and decreased in the colder half- year. The number of anticyclones increased by about 2.5% in those years, and practically all the increase took place in a warm half-year. The distribution functions are calculated for the size and kinetic energy of the vortices. These values are found by dimensional analysis in dependence on the energy, are found to be close to exponential ones. It is noted that the distribution functions for warmer 1990s differ from those for colder 1950s, with slightly more cyclones at present than half a century ago. Corresponding analysis will be presented for the INM RAS climate general circulation model in order to see how models of this kind can represent the distribution functions..