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Brunke M.A.,University of Arizona | Stegall S.T.,Cooperative Institute for Climate and Satellites | Zeng X.,University of Arizona
Atmospheric Research | Year: 2014

Specific humidity is generally thought to decrease with height in the troposphere. However, here we document the existence of specific humidity inversions in five reanalyses: the National Centers for Environmental Prediction (NCEP) second reanalysis (NCEP-2), the European Centre for Medium-Range Forecasts (ECMWF) 40-year reanalysis (ERA-40), the Modern Era Retrospective Analysis for Research Applications (MERRA), NCEP's Climate Forecast System Reanalysis (CFSR), and the ECMWF interim reanalysis (ERA-Interim). These inversions are most frequent in the polar regions. Inversions do occur elsewhere, most notably over the subtropical stratus regions, but are less frequent and likely overproduced depending on the location. Polar inversions are the most persistent in winter and the strongest (as defined by the humidity difference divided by the pressure difference across the inversion) in summer or autumn with low bases (at pressures. >. 900. hPa). Winter humidity inversions are lower, being near-surface, due to the persistence of low-level temperature inversions associated with these humidity inversions, while summer humidity inversions tend to be located near cloud top providing moisture to prevent the melt season stratus from evaporating. The most important contributions to affect humidity inversions in MERRA are dynamics, turbulence, and moist physics. However, local advection may not play as much of a role as regional humidity convergence. The subtropical stratus inversions are as thick as polar humidity inversions but with higher bases generally at pressures <. 900. hPa. These inversions are confirmed by rawinsonde data, but there are discrepancies between the observed annual and diurnal cycles in inversion frequency and those portrayed in the reanalyses. © 2014 Elsevier B.V. Source

Meyers P.C.,Cooperative Institute for Climate and Satellites
Journal of Geophysical Research: Oceans | Year: 2016

The 2008 Atlantic hurricane season featured two hurricanes, Gustav and Ike, crossing the Gulf of Mexico (GOM) within a 2 week period. Over 400 airborne expendable bathythermographs (AXBTs) were deployed in a GOM field campaign before, during, and after the passage of Gustav and Ike to measure the evolving upper ocean thermal structure. AXBT and drifter deployments specifically targeted the Loop Current (LC) complex, which was undergoing an eddy-shedding event during the field campaign. Hurricane Gustav forced a 50 m deepening of the ocean mixed layer (OML), dramatically altering the prestorm ocean conditions for Hurricane Ike. Wind-forced entrainment of colder thermocline water into the OML caused sea surface temperatures to cool by over 5°C in GOM common water, but only 1-2°C in the LC complex. Ekman pumping and a near-inertial wake were identified by fluctuations in the 20°C isotherm field observed by AXBTs and drifters following Hurricane Ike. Satellite estimates of the 20° and 26°C isotherm depths and ocean heat content were derived using a two-layer model driven by sea surface height anomalies. Generally, the satellite estimates correctly characterized prestorm conditions, but the two-layer model inherently could not resolve wind-forced mixing of the OML. This study highlights the importance of a coordinated satellite and in situ measurement strategy to accurately characterize the ocean state before, during, and after hurricane passage, particularly in the case of two consecutive storms traveling through the same domain. © 2015. American Geophysical Union. All Rights Reserved. Source

Peterson T.C.,National Oceanic and Atmospheric Administration | Heim Jr. R.R.,National Oceanic and Atmospheric Administration | Hirsch R.,U.S. Geological Survey | Kaiser D.P.,Oak Ridge National Laboratory | And 25 more authors.
Bulletin of the American Meteorological Society | Year: 2013

Some of the long-term changes in weather and climate extremes across the US have occurred as expected in the warming climate, but the trends vary throughout the country and easily detected due to multiyear and decadal variations. The US National Climate Assessment has to address extremes, as these are changing and anthropogenic climate change has a role in altering the probabilities of some of the extreme events. Extreme events also drive changes in natural and human systems more than average climatic conditions. Four workshops have been held to provide technical input to the US National Climate Assessment writing team where leading scientists in the field worked jointly to determine how best to assess the state of the science in understanding the decadal- to century-scale variability and changes in various types of extreme events. Source

Coopersmith E.J.,U.S. Department of Agriculture | Cosh M.H.,U.S. Department of Agriculture | Bindlish R.,Science Systems And Applications Inc. | Bell J.,Cooperative Institute for Climate and Satellites
Advances in Water Resources | Year: 2015

Soil moisture plays an integral role in multi-scale hydrologic modeling, agricultural decision analysis, climate change assessments, and drought prediction/prevention. The broad availability of soil moisture estimates has only occurred within the past decade through a combination of in situ networks and satellite-driven remote sensing. The U.S. Climate Reference Network (USCRN) has provided a nationwide in situ resource since 2009. The Advanced Microwave Scanning Radiometer (AMSR-E), launched in 2002, is one of the satellite products available for comparison, but there are a limited number of years where the data records overlap. This study compares the results of modeled historical soil moisture estimates derived using USCRN precipitation data to the remotely sensed estimates provided by the AMSR-E satellite between 2002 and 2011. First, this work assesses the calibrated model's similarity to in situ estimates. Next, the model estimates and in situ measurements are shown to perform comparably well against the AMSR-E satellite product, suggesting that it may be possible to utilize modeled estimates at times and locations where satellite estimates are unavailable and further extend the soil moisture record spatially and temporally. © 2015 Elsevier Ltd. Source

Vose R.S.,National Oceanic and Atmospheric Administration | Applequist S.,National Oceanic and Atmospheric Administration | Bourassa M.A.,Florida State University | Pryor S.C.,Indiana University Bloomington | And 22 more authors.
Bulletin of the American Meteorological Society | Year: 2014

Weather and climate extremes profoundly affect society and the environment, resulting in the loss of life, property, and habitat. The extremes discussed herein are causally related: extratropical storms account for the majority of extreme winds during the cold season, and extreme waves are largely driven by extreme winds. For assessment purposes, extremes are defined based on meteorological principles rather than physical destructiveness. Nevertheless, each of these extremes can result in substantial societal impacts. Estimates of extratropical storm activity primarily derive from two sources: atmospheric reanalyses and pressure-based indices. Reanalysis products have the advantage of uniform space and time fields on which to locate pressure minima or vorticity maxima, facilitating the identification of storm tracks. In contrast, pressure-based indices have the advantage of being directly computed from in situ observations, which often extend further back in time than most reanalyses. Source

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