A Note on Reviving the Goddard Satellite-Based Surface Turbulent Fluxes (GSSTF) Dataset

Accurate sea surface flux measurements are crucial for understanding the global water and energy cycles. The oceanic evaporation, which is a major component of the global oceanic fresh water flux, is useful for predicting oceanic circulation and transport. The global Goddard Satellite-based Surface Turbulent Fluxes Version-2 （GSSTF2; July 1987–December 2000） dateset that was o？cially released in 2001 has been widely used by scientific community for global energy and water cycle research, and regional and short period data analyses. We have recently been funded by NASA to resume processing the GSSTF dataset with an objective of continually producing a uniform dataset of sea surface turbulent fluxes, derived from remote sensing data. The dataset is to be reprocessed and brought up-to-date （GSSTF2b） using improved input datasets such as a recently upgraded NCEP/DOE sea surface temperature reanalysis, and an upgraded surface wind and microwave brightness temperature V6 dataset （Version 6） from the Special Sensor Microwave Imager （SSM/I） produced by Remote Sensing Systems （RSS）. A second new product （GSSTF3） is further proposed with a finer temporal （12-h） and spatial （0.25° × 0.25°） resolution. GSSTF2b （July 1987–December 2008） and GSSTF3 （July 1999–December 2009） will be released for the research community to use by late 2009 and early 2011, respectively.

A Parameterization Scheme of Surface Turbulent Momentum and Sensible Heat over the Gobi Underlying Surface

The parameterization of surface turbulent fluxes over the Gobi Desert in arid regions is studied by using rationally screened observational data. First, the characteristics of Monin-Obukhov similarity functions are analyzed and their empirical formulae are fitted. The results show that fitted curves of changes of similarity functions of wind speed and temperature with stability parameter differ little from the typical empirical curves and are within the ranges of scatter of the empirical curves, but their values in the neutral condition arc different from the typical values to some extent. Furthermore, average values of momentum and scalar (sensible heat) roughness lengths as well as changes of scalar roughness length with friction velocity are determined by utilizing the data. It is found that the average values of scalar roughness length are about one order smaller than that of the momentum roughness length and decrease with increasing friction velocity, but they are evidently larger than their theoretically forecasted values.

Global Land Surface Climate Analysis Based on the Calculation of a Modified Bowen Ratio

A modified Bowen ratio(BRm),the sign of which is determined by the direction of the surface sensible heat flux,was used to represent the major divisions in climate across the globe,and the usefulness of this approach was evaluated. Five reanalysis datasets and the results of an offline land surface model were investigated. We divided the global continents into five major BRm zones using the climatological means of the sensible and latent heat fluxes during the period 1980–2010:extremely cold,extremely wet,semi-wet,semi-arid and extremely arid. These zones had BRm ranges of(-∞,0),(0,0.5),(0.5,2),(2,10) and(10,+∞),respectively. The climatological mean distribution of the Bowen ratio zones corresponded well with the K ¨oppen-like climate classification,and it reflected well the seasonal variation for each subdivision of climate classification. The features of climate change over the mean climatological BRm zones were also investigated. In addition to giving a map-like classification of climate,the BRm also reflects temporal variations in different climatic zones based on land surface processes. An investigation of the coverage of the BRm zones showed that the extremely wet and extremely arid regions expanded,whereas a reduction in area was seen for the semi-wet and semi-arid regions in boreal spring during the period 1980–2010. This indicates that the arid regions may have become drier and the wet regions wetter over this period of time.

A Method for Improving Simulation of PNA Teleconnection Interannual Variation in a Climate Model

The climate modeling community has been challenged to develop a method for improving the simulation of the Pacific-North America （PNA） teleconnection pattern in climate models. The accuracy of PNA teleconnection simulation is significantly improved by considering mesoscale convection contributions to sea surface fluxes. The variation in the PNA over the past 22 years was simulated by the Grid Atmospheric Model of lAP LASG version 1.0 （GAMIL1.0）, which was guided by observational SST from January 1979 to December 2000. Results show that heating in the tropical central-eastern Pacific is simulated more realistically, and sea surface latent heat flux and precipitation anomalies are more similar to the reanalysis data when mesoscale enhancement is considered during the parameterization scheme of sea surface turbulent fluxes in GAMIL1.0. Realistic heating in the tropical central-eastern Pacific in turn significantly improves the simulation of interannual variation and spatial patterns of PNA.

Possible Links between Arctic Sea Ice Loss Events and Cold Eurasian Anomalies in Winter

Recently,there have been two competing perspectives on the links of rapid sea ice retreat over the Barents–Kara Seas(BKS)and in midlatitude severe cold winters over Eurasia.By using the daily ECMWF reanalysis(ERA)-Interim dataset during 1979–2016,we reconcile two contrasting viewpoints,namely,if an upward turbulent heat flux appears and maintains several days after the rapid sea ice loss over the BKS in winter,a dipole structure which consists of a primary positive center of action around the Barents Sea with the other opposite-sign center of action over Eurasian continent is easily amplified,and consequently a cold anomaly over Eurasia will occur,but not vice versa.Our work casts light on the links between the Arctic sea ice loss and Eurasian cold winter anomalies by revealing the different responses of the surface turbulent heat flux(STHF)after rapid sea ice retreat on a daily basis.