5 results on '"Uma S Bhatt"'
Search Results
2. A novel method to simulate AVIRIS-NG hyperspectral image from Sentinel-2 image for improved vegetation/wildfire fuel mapping, boreal Alaska
- Author
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Anushree Badola, Santosh K. Panda, Dar A. Roberts, Christine F. Waigl, Randi R. Jandt, and Uma S. Bhatt
- Subjects
Global and Planetary Change ,Management, Monitoring, Policy and Law ,Computers in Earth Sciences ,Earth-Surface Processes - Published
- 2022
- Full Text
- View/download PDF
3. Downscaling of climate model output for Alaskan stakeholders
- Author
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Peter A. Bieniek, Jeremy S. Littell, John Walsh, T. A. Kurkowski, Michael Lindgren, Richard Thoman, Uma S. Bhatt, Matthew Leonawicz, T. Scott Rupp, and Stephen T. Gray
- Subjects
Software visualization ,Environmental Engineering ,Forcing (recursion theory) ,010504 meteorology & atmospheric sciences ,Meteorology ,Computer science ,Ecological Modeling ,0208 environmental biotechnology ,Northern Hemisphere ,02 engineering and technology ,01 natural sciences ,020801 environmental engineering ,Visualization ,Range (statistics) ,Climate model ,Precipitation ,Software ,0105 earth and related environmental sciences ,Downscaling - Abstract
The paper summarizes an end-to-end activity connecting the global climate modeling enterprise with users of climate information in Alaska. The effort included retrieval of the requisite observational datasets and model output, a model evaluation and selection procedure, the actual downscaling by the delta method with its inherent bias-adjustment, and the provision of products to a range of users through visualization software that empowers users to explore the downscaled output and its sensitivities. An additional software tool enables users to examine skill metrics and relative rankings of 21 global models for Alaska and six other domains in the Northern Hemisphere. The downscaled temperatures and precipitation are made available as calendar-month decadal means under three different greenhouse forcing scenarios through 2100 for more than 4000 communities in Alaska and western Canada. The visualization package displays the uncertainties inherent in the multi-model ensemble projections. These uncertainties are often larger than the projected changes.
- Published
- 2018
- Full Text
- View/download PDF
4. Surface-based temperature inversions in Alaska from a climate perspective
- Author
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Richard Thoman, Jing Zhang, Uma S. Bhatt, and S. M. Bourne
- Subjects
Climate zones ,Atmospheric Science ,cvg.computer_videogame ,Inversion (meteorology) ,King salmon ,Atmospheric temperature ,law.invention ,law ,Climatology ,Radiosonde ,Temperature difference ,cvg ,Inversion temperature ,Pacific decadal oscillation ,Geology - Abstract
Alaska surface-based temperature inversions were analyzed using radiosonde observations from Barrow, Fairbanks, McGrath, Anchorage, Kotzebue, Bethel and King Salmon, which represent different climate zones in Alaska. Inversion climatology, variability and links to the large-scale climate were investigated for the period of 1957–2008 when high quality radiosonde data are available. Inversion parameters, such as depth, temperature difference, and frequency, have a long-term decreasing trend, which is not simply linear but displays multi-decadal variations. Inversion depth decreased from 1957 to the late 1980s and has been increasing since. The multi-decadal signal has been detected at all stations but is particularly dominant for Interior stations. The relationship between Alaska inversion and the Pacific Decadal Oscillation changes over time and was found to be stronger before 1989 than in recent years. Alaska inversions also demonstrate strikingly similar interannual variability, suggesting an important role of large-scale circulation.
- Published
- 2010
- Full Text
- View/download PDF
5. Influence of North American land processes on North Atlantic Ocean variability
- Author
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Edwin K. Schneider, Uma S. Bhatt, and David G. DeWitt
- Subjects
Atmosphere ,Global and Planetary Change ,Sea surface temperature ,Heat flux ,Moisture ,Mixed layer ,Climatology ,Anomaly (natural sciences) ,Middle latitudes ,Environmental science ,Oceanography ,Atmospheric temperature - Abstract
A set of numerical simulations has been carried out to evaluate the influence of coupled land–atmosphere and ocean–atmosphere interactions on natural climate variability. The baseline experiment was a long integration of a state-of-the-art-coupled atmosphere–ocean–land general circulation model (GCM). A sensitivity experiment was conducted in which the ocean and atmosphere were fully interactive but the soil moisture was specified. This paper describes a connection found between land–atmosphere coupling and midlatitude sea surface temperature (SST) variability in the North American–North Atlantic sector. Specifying soil moisture results in a reduction in surface and atmospheric temperature variability and also an increase in net heat flux variability. Surface temperature variance is reduced because it is constrained by the fixed soil moistures. Since the surface temperature cannot equilibrate with a given atmospheric anomaly, the resulting heat flux will be quite large and will act to damp the atmospheric anomaly. This is consistent with larger heat flux variance and reduced temperature variance in the simulation with suppressed land processes. SST anomalies in the midlatitude Atlantic are sensitive to air temperature and moisture anomalies modified over the North American continent, so it is not unexpected that SST variance is significantly reduced when land temperature variability decreases. Oceanic ‘re-emergence’ operates in both simulations but is weaker in the fixed soil moisture integration, particularly in a region of the western North Atlantic contiguous with North America. Reemergence is the mechanism by which late winter ocean temperature anomalies are sequestered below the stable summer ocean mixed layer and reentrained into the deepening autumn mixed layer. The larger oceanic anomalies in the fully coupled simulation decay more slowly and are a partial explanation for stronger reemergence. However, during the second winter, the atmospheric forcing favors the same sign of SST anomalies as those reemerging and, therefore, acts to reinforce the anomalies in the fully coupled simulation. An area averaged SST index was constructed for the region of the western North Atlantic where reemergence was most notably reduced. This index was used to construct composites which suggest that, in the fully coupled model, land surface temperature and SST anomalies both reemerge the second winter, whereas in the suppressed land processes simulation, there is no winter-to-winter reappearance of land surface temperature anomalies. The late winter land temperatures are able to reemerge in fall because of the persistence of soil moisture anomalies.
- Published
- 2003
- Full Text
- View/download PDF
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