Trends and variations of ocean surface latent heat flux: Results from GSSTF2c data set

Si, Gangyan; Chiu, Long S.; Shie, Chung‐Lin

doi:10.1029/2012gl054620

Cited by 18 publications

(11 citation statements)

References 33 publications

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“…Since the changes in the sea ice concentration cause changes in the surface temperature and hence the surface‐specific humidity, hence changing the magnitude of ( q s ‐ q z ), we can therefore attribute changes to evaporation to changes in ( q s ‐ q z ) and in the 10‐m wind speed. From Figure , it is clear that the changes in the wind speed and humidities are decoupled; we can then follow Gao et al () to determine the contribution of each of these variables to the change in evaporation between 2003 and 2016. Specifically, (1) can be integrated to get (3) by ignoring any changes made in the transfer coefficient:

\frac{δ \overset{E}{true}}{\overset{true¯}{E}} \approx \frac{δ \overset{U}{true}}{\overset{true¯}{U}} + \frac{δ \overset{Q}{true}}{\overset{true¯}{Q}}

where

δ \overset{Q}{true} = δ \overset{q_{s}}{true} - δ \overset{q_{z}}{true}

is the specific humidity, U is the wind speed,

δ \overset{x}{true}

is the change in the variable x , and

\frac{δ \overset{x}{true}}{\overset{true¯}{x}}

is the fractional change (i.e., the trend) of each variable.…”

Section: Southern Ocean Evaporation Trendsmentioning

confidence: 98%

Evaporation From the Southern Ocean Estimated on the Basis of AIRS Satellite Data

2020

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Evaporation plays an important role in the global water and energy cycles and, hence, in climate change. Evaporation over the Southern Ocean, where the Antarctic sea ice coverage has a large annual cycle, is poorly quantified. In this study, daily evaporation is estimated for the Southern Ocean with a sea-ice-specific algorithm, using surface temperature and air humidity from National Aeronautics and Space Administration's Atmospheric Infrared Sounder (AIRS), and wind speeds from Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2), reanalysis during 2003-2016. An uncertainty of 34% was found in the evaporation product. The results indicate that annual evaporation has considerable interannual and regional variability, but with a decreasing trend during the study period over most of the Southern Ocean. There are, however, areas where evaporation has increased, specifically in the Ross Sea in winter and summer, with smaller positive trends in spring and fall. Overall, the changes in the difference between the surface specific humidity and the air specific humidity, and to a much lesser extent in the wind speed, are the main drivers for the changes in evaporation throughout the year. During spring and fall months, changes to the sea ice cover, which alter the surface specific humidity, are the main drivers for the change, but in summer and winter the main driver is the air-specific humidity. Air masses originating from the Antarctic continent (south) are associated with cold and dry conditions, which increase evaporation, whereas air masses from lower latitudes in the Southern Ocean (north) are associated with warm and moist conditions, decreasing evaporation. Comparisons with other reanalysis evaporation products produce similar trends, although annual averages differ.

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\frac{δ \overset{E}{true}}{\overset{true¯}{E}} \approx \frac{δ \overset{U}{true}}{\overset{true¯}{U}} + \frac{δ \overset{Q}{true}}{\overset{true¯}{Q}}

where

δ \overset{Q}{true} = δ \overset{q_{s}}{true} - δ \overset{q_{z}}{true}

is the specific humidity, U is the wind speed,

δ \overset{x}{true}

is the change in the variable x , and

\frac{δ \overset{x}{true}}{\overset{true¯}{x}}

is the fractional change (i.e., the trend) of each variable.…”

Section: Southern Ocean Evaporation Trendsmentioning

confidence: 98%

Evaporation From the Southern Ocean Estimated on the Basis of AIRS Satellite Data

2020

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“…However, these products differ considerably from each other (Gao et al 2013). A large portion of the errors in these products is found to be associated with uncertainties in the near-surface Qa and Ta, as these nearsurface atmosphere properties cannot be directly sensed from satellites, and retrieval algorithms are very different and all have uncertainties (Curry et al 2004;Jackson et al 2006;Jackson and Wick 2010;Roberts et al 2010).…”

Section: Introductionmentioning

confidence: 95%

An Improved Near-Surface Specific Humidity and Air Temperature Climatology for the SSM/I Satellite Period

Jin

Jackson

et al. 2015

Journal of Atmospheric and Oceanic Technology

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A near-surface specific humidity (Qa) and air temperature (Ta) climatology on daily and 0.258 grids was constructed by the objectively analyzed air-sea fluxes (OAFlux) project by objectively merging two recent satellite-derived high-resolution analyses, the OAFlux existing 18 analysis, and atmospheric reanalyses. The two satellite products include the multi-instrument microwave regression (MIMR) Qa and Ta analysis and the Goddard Satellite-Based Surface Turbulent Fluxes, version 3 (GSSTF3), Qa analysis. This study assesses the degree of improvement made by OAFlux using buoy time series measurements at 137 locations and a global empirical orthogonal function (EOF) analysis. There are a total of 130 855 collocated daily values for Qa and 283 012 collocated daily values for Ta in the buoy evaluation. It is found that OAFlux Qa has a mean difference close to 0 and a root-mean-square (RMS) difference of 0.73 g kg 21, and Ta has a mean difference of 20.038C and an RMS difference of 0.458C. OAFlux shows no major systematic bias with respect to buoy measurements over all buoy locations except for the vicinity of the Gulf Stream boundary current, where the RMS difference exceeds 1.88C in Ta and 1.2 g kg 21 in Qa. The buoy evaluation indicates that OAFlux represents an improvement over MIMR and GSSTF3. The global EOF-based intercomparison analysis indicates that OAFlux has a similar spatial-temporal variability pattern with that of three atmospheric reanalyses including MERRA, NCEP-1, and ERA-Interim, but that it differs from GSSTF3 and the Climate Forecast System Reanalysis (CFSR).

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“…More recently, Gao et al . [] examined latent heat flux trends between 1988 and 2008 using the Goddard Satellite‐based Surface Turbulent Fluxes version 2c (GSSTF2c). They found particularly strong (∼10 Wm −2 /decade) trends over the western boundary currents but also in the subtropics of the southern hemisphere.…”

Section: Introductionmentioning

confidence: 99%

“…The trend patterns for 1977-2006 found in the tropical and subtropical Pacific by Li et al [2011] were also consistent with this picture. More recently, Gao et al [2013] examined latent heat flux trends between 1988 and 2008 using the Goddard Satellite-based Surface Turbulent Fluxes version 2c (GSSTF2c). They found particularly strong ($10 Wm 22 /decade) trends over the western boundary currents but also in the subtropics of the southern hemisphere.…”

Section: Introductionmentioning

confidence: 99%

Assessing recent air-sea freshwater flux changes using a surface temperature-salinity space framework

Grist

Josey

Zika

et al. 2016

J. Geophys. Res. Oceans

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A novel assessment of recent changes in air‐sea freshwater fluxes has been conducted using a surface temperature‐salinity framework applied to four atmospheric reanalyses. Viewed in the T‐S space of the ocean surface, the complex pattern of the longitude‐latitude space mean global Precipitation minus Evaporation (PME) reduces to three distinct regions. The analysis is conducted for the period 1979–2007 for which there is most evidence for a broadening of the (atmospheric) tropical belt. All four of the reanalyses display an increase in strength of the water cycle. The range of increase is between 2% and 30% over the period analyzed, with an average of 14%. Considering the average across the reanalyses, the water cycle changes are dominated by changes in tropical as opposed to mid‐high latitude precipitation. The increases in the water cycle strength, are consistent in sign, but larger than in a 1% greenhouse gas run of the HadGEM3 climate model. In the model a shift of the precipitation/evaporation cells to higher temperatures is more evident, due to the much stronger global warming signal. The observed changes in freshwater fluxes appear to be reflected in changes in the T‐S distribution of the Global Ocean. Specifically, across the diverse range of atmospheric reanalyses considered here, there was an acceleration of the hydrological cycle during 1979–2007 which led to a broadening of the ocean's salinity distribution. Finally, although the reanalyses indicate that the warm temperature tropical precipitation dominated water cycle change, ocean observations suggest that ocean processes redistributed the freshening to lower ocean temperatures.

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Trends and variations of ocean surface latent heat flux: Results from GSSTF2c data set

Cited by 18 publications

References 33 publications

Evaporation From the Southern Ocean Estimated on the Basis of AIRS Satellite Data

Evaporation From the Southern Ocean Estimated on the Basis of AIRS Satellite Data

An Improved Near-Surface Specific Humidity and Air Temperature Climatology for the SSM/I Satellite Period

Assessing recent air-sea freshwater flux changes using a surface temperature-salinity space framework

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