- Using Soil Moisture Observations to Study Climate Variations, to Evaluate Climate Models, and as Ground Truth for Remote Sensing
- Soil moisture is an important variable in the climate system. Understanding and predicting variations of surface temperature, drought, and flood depend critically on knowledge of soil moisture variations, as do impacts of climate change and seasonal forecasting. An observational data set of actual in situ measurements is crucial for model development and evaluation, and as ground truth for remote sensing. I will describe the Global Soil Moisture Data Bank, a web site (http://envsci.rutgers.edu/~robock/) dedicated to collection, dissemination, and analysis of soil moisture data from around the globe. The Global Soil Moisture Data Bank is a resource for the remote sensing, climate modeling and climate analysis communities. We currently have soil moisture observations for over 400 stations from a large variety of global climates, including from the former Soviet Union, China, Mongolia, India, and the US. I will give examples of several different uses of these data sets. These include the analysis of interseasonal, interannual and interdecadal variations in soil moisture, determination of the important scales of soil moisture variations, and the application of this result to the representativeness of our current soil moisture network and to recommendations about spatial and temporal scales of climate modeling and satellite remote sensing of soil moisture. We also use these data to evaluate calculations of soil moisture by land surface models, including PILPS Phase 2(d), reanalyses, AMIP, and the Global Soil Wetness Experiment, and as ground truth for passive microwave remote sensing of soil moisture. The scale of temporal variation of soil moisture observed in Illinois, Russia, China, and Mongolia is about 2 months in all cases and the spatial scale in all these regions is about 500 km. These scales are controlled by atmospheric forcing. Therefore, the new soil moisture network in Oklahoma is exceedingly dense for climate applications, but may be fine for initializing short-term weather forecasts. Most land surface schemes have a hard time simulating the actual observed seasonal and interannual variations of soil moisture, but produce anomalies that are close to observations. Upward trends of summer soil moisture are observed in Russia and Mongolia. Remote sensing using SMMR data over Illinois produces quite good results.
- Volcanic Eruptions and Climate: Winter Warming and Summer Cooling
- Large volcanic eruptions inject sulfur gases into the stratosphere, which convert to sulfate aerosols with an e-folding residence time of about 1 year. Large ash particles fall out much quicker. The radiative and chemical effects of this aerosol cloud produce responses in the climate system. By scattering some solar radiation back to space, the aerosols cool the surface, but by absorbing both solar and terrestrial radiation, the aerosol layer heats the stratosphere. For a tropical eruption, this heating is larger in the tropics than in the high latitudes, producing an enhanced pole-to-equator temperature gradient, especially in winter. During the winter in the Northern Hemisphere following every large tropical eruption of the past century, surface air temperatures over North America, Europe, and East Asia were warmer than normal, while they were colder over Greenland and the Middle East. This pattern and the coincident atmospheric circulation correspond to the positive phase of the Arctic Oscillation. In spite of the decrease in surface solar heating, surface air temperature increases in high and midlatitudes of the Northern Hemisphere in the winter because of changes in tropospheric circulation caused by stratosphere-troposphere dynamical coupling. Using the Max Planck Institute ECHAM4 and the Geophysical Fluid Dynamics Laboratory SKYHI GCMs, we have successfully simulated this response following the 1991 Mount Pinatubo eruption. This result will allow us to produce better seasonal forecasts for the Northern Hemisphere winter following the next large tropical eruption. It also shows that stratospheric forcing of the climate system must be considered along with sea surface temperature anomalies when making seasonal forecasts, especially in mid and high latitudes in the winter.
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$B!V(BStudy on the Estimation of Global Soil Erosion$B!W(B$B$G$9!#(B
9:30 $B3+2q$N<-(B $BC]Fb(B $BK.NI(B 9:40 $B $BCnL@(B $B8y?C(B 10:00 $BBh0lIt(B $B?e$H2J3X$r$a$0$kAm9gE*9q:]>p@*(B Water under pressure John Rodda (IAHS) Current and expected international research priorities in hydrology Andras Szollosi-Nagy (UNESCO) Science and and operational practice -- a powerful partnership Arthur Askew (WMO) 11:30 $BBhFsIt(B Perception of risk of flooding, case of 1995 floods in Norway Irina Krasovskaia (Norway) Water problems of Eastern Europe, a region-in-transition Zbigniew Kundzewicz (Poland) 13:30 $BBhFsIt(B($BB3$-(B) Water problems and opportunities in hydrological sciences in China Xia Jun (China) Challenges and opportunities for water resources management in South-East Asia Ashim Das Gupta (Thailand) Some scientific challenges in Southe American water resources development Carlos Tucci (Brazil) Water problems in Africa: how can hydrological sciences help? Lekan Oyebande (Nigeria) 16:00 $BBh;0It(B Regional/Macro-scale hydrological modelling - a Scandinavian experience Lars Gottschalk (Norway) Multifractals as a tool to overcome scale problems in hydrology Pierre Hubert (France) World Water Development Report and World Water Assessment Program Gordon Young (UNESCO)