Monthly Climatologies of Oceanic Friction Velocity Cubed

2006 ◽  
Vol 19 (21) ◽  
pp. 5700-5708 ◽  
Author(s):  
Barry A. Klinger ◽  
Bohua Huang ◽  
Ben Kirtman ◽  
Paul Schopf ◽  
Jiande Wang
Keyword(s):  
Wind Speed ◽  
Wind Stress ◽  
Friction Velocity ◽  
Turbulent Energy ◽  
Data Set ◽  
Wind Influence ◽  
Satellite Microwave ◽  
Environmental Prediction ◽  
Satellite Microwave Measurements ◽  
The Tropics

Abstract Different measures of wind influence the ocean in different ways. In particular, the time-averaged mixed layer turbulent energy production rate is proportional to 〈u3*〉, where u* is the “oceanic friction velocity” that is based on wind stress. Estimating 〈u3*〉 from monthly averages of wind stress or wind speed may introduce large biases due to the day-to-day variability of the direction and magnitude of the wind. The authors create monthly climatologies of 〈u3*〉 from daily wind stress measurements obtained from the Goddard Satellite-based Surface Turbulent Fluxes version 2 (GSSTF2; based on satellite microwave measurements), the Quick Scatterometer (QuikSCAT; based on satellite scatterometry measurements), and the National Centers for Environmental Prediction (NCEP) reanalysis wind. The differences among zonal averages of these climatologies and of a similar climatology based on the da Silva version of the Comprehensive Ocean–Atmosphere Data Set (COADS) have a complex dependence on latitude. These differences are typically 10%–30% of the climatological values. The GSSTF2 data confirm that 〈u3*〉 is much larger than estimates from monthly averaged wind stress or wind speed, especially outside the Tropics.

Statistical Characterization of Zonal and Meridional Ocean Wind Stress

2005 ◽  
Vol 22 (9) ◽  
pp. 1353-1372 ◽  
Author(s):  
Sarah T. Gille
Keyword(s):  
Wind Stress ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
Statistical Characterization ◽  
Weather Forecasts ◽  
The Pacific ◽  
Meridional Winds ◽  
Wind Events ◽  
Environmental Prediction ◽  
The Tropics

Abstract Four years of ocean vector wind data are used to evaluate statistics of wind stress over the ocean. Raw swath wind stresses derived from the Quick Scatterometer (QuikSCAT) are compared with five different global gridded wind products, including products based on scatterometer observations, meteorological analysis winds from the European Centre for Medium-Range Weather Forecasts, and reanalysis winds from the National Centers for Environmental Prediction. Buoy winds from a limited number of sites in the Pacific Ocean are also considered. Probability density functions (PDFs) computed for latitudinal bands show that mean wind stresses for the six global products are largely in agreement, while variances differ substantially, by a factor of 2 or more, with swath wind stresses indicating highest variances for meridional winds and for zonal winds outside the Tropics. Higher moments of the PDFs also differ. Kurtoses are large for all wind products, implying that PDFs are not Gaussian. None of the available gridded products fully captures the range of extreme wind events seen in the raw swath data. Frequency spectra for the five gridded products agree with frequency spectra from swath data at low frequencies, but spectral slopes differ at higher frequencies, particularly for frequencies greater than 100 cycles per year (cpy), which are poorly resolved by a single scatterometer. In the frequency range between 10 and 90 cpy that is resolved by the scatterometer, spectra derived from swath data are flatter than spectra from gridded products and are judged to be flatter than ω−2/3 at all latitudes.

scholarly journals Toward a long-term homogenized UTH data set derived from satellite microwave measurements

2006 ◽  
Author(s):  
V. O. John ◽  
S. A. Buehler ◽  
M. Kuvatov ◽  
B. J. Soden ◽  
T. R. Sreerekha
Keyword(s):  
Microwave Measurements ◽  
Data Set ◽  
Satellite Microwave ◽  
Satellite Microwave Measurements

scholarly journals Description of the ERA-CLIM historical upper-air data

2014 ◽  
Vol 6 (1) ◽  
pp. 29-48 ◽  
Author(s):  
A. Stickler ◽  
S. Brönnimann ◽  
S. Jourdain ◽  
E. Roucaute ◽  
A. Sterin ◽  
...  
Keyword(s):  
Global Climate ◽  
Current Status ◽  
Polar Regions ◽  
Data Set ◽  
International Geophysical Year ◽  
The Us ◽  
Environmental Prediction ◽  
The Tropics ◽  
Source Of Information ◽  
International Geophysical

Abstract. Historical, i.e. pre-1957, upper-air data are a valuable source of information on the state of the atmosphere, in some parts of the world dating back to the early 20th century. However, to date, reanalyses have only partially made use of these data, and only of observations made after 1948. Even for the period between 1948 (the starting year of the NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis) and the International Geophysical Year in 1957 (the starting year of the ERA-40 reanalysis), when the global upper-air coverage reached more or less its current status, many observations have not yet been digitised. The Comprehensive Historical Upper-Air Network (CHUAN) already compiled a large collection of pre-1957 upper-air data. In the framework of the European project ERA-CLIM (European Reanalysis of Global Climate Observations), significant amounts of additional upper-air data have been catalogued (> 1.3 million station days), imaged (> 200 000 images) and digitised (> 700 000 station days) in order to prepare a new input data set for upcoming reanalyses. The records cover large parts of the globe, focussing on, so far, less well covered regions such as the tropics, the polar regions and the oceans, and on very early upper-air data from Europe and the US. The total number of digitised/inventoried records is 61/101 for moving upper-air data, i.e. data from ships, etc., and 735/1783 for fixed upper-air stations. Here, we give a detailed description of the resulting data set including the metadata and the quality checking procedures applied. The data will be included in the next version of CHUAN. The data are available at doi:10.1594/PANGAEA.821222.

scholarly journals Air-sea momentum flux climatologies: A review of drag relation for parameterization choice on wind stress in the North Atlantic and the European Arctic

2018 ◽  
Author(s):  
Iwona Wrobel-Niedzwiecka ◽  
Violetta Drozdowska ◽  
Jacek Piskozub
Keyword(s):  
Wind Speed ◽  
Drag Coefficient ◽  
Wind Stress ◽  
North Atlantic ◽  
Momentum Flux ◽  
The Arctic ◽  
The North ◽  
European Arctic ◽  
The North Atlantic ◽  
The Tropics

Abstract. In this paper we have chosen to check the differences between the relevant or most commonly used parameterizations for drag coefficient (CD) for the momentum transfer values, especially in the North Atlantic (NA) and the European Arctic (EA). As is well know, the exact equation in the North equation that describes the connection betwenn the drag coefficient and wind speed depends on the author. We studied monthly values of air-sea momentum flux resulting from the choice of different drag coefficient parameterizations, adapted them to momentum flux (wind stress) calculations using SAR wind fields, sea-ice masks, as well as integrating procedures. We calculated monthly momentum flux averages on a 1º x 1º degree grid and derive average values for the North Atlantic and the European Arctic. We compared the resulting spreads in momentum flux to global values and values in the tropics, an area of prevailing low winds. We show that the choice of drag coefficient parameterization can lead to significant differences in resultant momentum flux (or wind stress) values. We found that the spread of results stemming from the choice of drag coefficient parameterization was 14 % in the Arctic, the North Atlantic and globally, but it was higher (19 %) in the tropics. On monthly time scales, the differences were larger at up to 29 % in the North Atlantic and 36 % in the European Arctic (in months of low winds) and even 50 % locally (the area west of Spitsbergen). When we chose the oldest parameterization (e.g Wu, 1969 (W69)) values of momentum flux were largest for all months, in compare to values from the two newest parameterizations (Large and Yeager, 2004 (LY04) and Andreas, 2012 (A12)), in both regions with high and low winds and CD values were consistently higher for all wind speeds. For global data not much seasonal change was note due to the fact that the strongest winds are in autumn and winter as these seasons are inverse by six months for the northern and southern hemispheres. The situation was more complicated when we considered results from the North Atlantic, as the seasonal variation in wind speed is clearly marked out there. With high winter winds, the A12 parameterization was no longer the one that produces the smallest wind stress. In this region, in summer, the highest wind stress values were produced by the NCEP/NCAR reanalysis, where in CD has a constant value. However, for low summer winds, it is the lowermost outlier. As the A12 parameterization behaves so distinctly differently with low winds, we showed seasonal results for the tropical ocean. The sequence of values for the parameterization was similar to that of the global ocean, but with visible differences betwenn NCEP/NCAR, A12 and LY04 parameterizaions. Because parameterization is supported with the largest experimental data set observations of very low (or even negative) momentum flux values for developed swell and low winds, our results suggest that most circulation models overestimate momentum flux.

scholarly journals Global carbonyl sulfide (OCS) measured by MIPAS/Envisat during 2002–2012

2016 ◽  
Author(s):  
Norbert Glatthor ◽  
Michael Höpfner ◽  
Adrian Leyser ◽  
Gabriele P. Stiller ◽  
Thomas von Clarmann ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Michelson Interferometer ◽  
Austral Summer ◽  
Emission Spectra ◽  
Set Covering ◽  
Boreal Summer ◽  
Systematic Bias ◽  
High Latitudes ◽  
Data Set ◽  
The Tropics

Abstract. We present a global OCS data set covering the period June 2002 to April 2012, derived from FTIR limb emission spectra measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the ENVISAT satellite. The vertical resolution is 4–5 km in the height region 6–15 km and 15 km at 40 km altitude. The total estimated error amounts to 40–50 pptv between 10 and 20 km and to 120 pptv at 40 km altitude. MIPAS OCS data show no systematic bias with respect to balloon observations, with deviations mostly below ±50 pptv. However, they are systematically higher than the OCS volume mixing ratios of the ACE-FTS instrument on SCISAT, with maximum deviations of up to 100 pptv in the altitude region 13–16 km. The data set of MIPAS OCS exhibits only moderate interannual variations and low interhemispheric differences. Average concentrations at 10 km altitude range from 480 pptv at high latitudes to 500–510 pptv in the tropics and at northern mid-latitudes. Seasonal variations at 10 km altitude amount up to 35 pptv in the northern and up to 15 pptv in the southern hemisphere. Northern hemispheric OCS abundances at 10 km altitude peak in June in the tropics and around October at high latitudes, while the respective southern hemispheric maxima were observed in July and in November. Global OCS distributions at 250 hPa (~ 10–11 km) show enhanced values at low latitudes, peaking during boreal summer above the western Pacific and the Indian Ocean, which indicates oceanic release. Further, a region of depleted OCS amounts extending from Brazil to central and southern Africa was detected at this altitude, which is most pronounced in austral summer. This depletion is related to seasonally varying vegetative uptake by the tropical forests. Typical signatures of biomass burning like the southern hemispheric biomass burning plume are not visible in MIPAS data, indicating that this process is only a minor source of tropospheric OCS. At the 150 hPa level (~ 13–14 km) enhanced amounts of OCS were also observed inside the Asian Monsoon Anticyclone, but this enhancement is not especially outstanding as compared to other low latitude regions at the same altitude. At the 80 hPa level (~ 17–18 km) equatorward transport of mid-latitude air masses containing lower OCS amounts around the summertime anticyclones was observed. A significant trend could not be detected in tropospheric MIPAS OCS amounts, which points to globally balanced sources and sinks.

scholarly journals Wind Speed Retrieval from Simulated RADARSAT Constellation Mission Compact Polarimetry SAR Data for Marine Application

2019 ◽  
Vol 11 (14) ◽  
pp. 1682 ◽  
Author(s):  
Torsten Geldsetzer ◽  
Shahid K. Khurshid ◽  
Kerri Warner ◽  
Filipe Botelho ◽  
Dean Flett
Keyword(s):  
Wind Speed ◽  
Low Noise ◽  
Quality Data ◽  
Band Model ◽  
Data Set ◽  
Wind Retrieval ◽  
Wind Speeds ◽  
Geophysical Model ◽  
The Right ◽  
Quality Threshold

RADARSAT Constellation Mission (RCM) compact polarimetry (CP) data were simulated using 504 RADARSAT-2 quad-pol SAR images. These images were used to samples CP data in three RCM modes to build a data set with co-located ocean wind vector observations from in situ buoys on the West and East coasts of Canada. Wind speeds up to 18 m/s were included. CP and linear polarization parameters were related to the C-band model (CMOD) geophysical model functions CMOD-IFR2 and CMOD5n. These were evaluated for their wind retrieval potential in each RCM mode. The CP parameter Conformity was investigated to establish a data-quality threshold (>0.2), to ensure high-quality data for model validation. An accuracy analysis shows that the first Stokes vector (SV0) and the right-transmit vertical-receive backscatter (RV) parameters were as good as the VV backscatter with CMOD inversion. SV0 produced wind speed retrieval accuracies between 2.13 m/s and 2.22 m/s, depending on the RCM mode. The RCM Medium Resolution 50 m mode produced the best results. The Low Resolution 100 m and Low Noise modes provided similar results. The efficacy of SV0 and RV imparts confidence in the continuity of robust wind speed retrieval with RCM CP data. Three image-based case studies illustrate the potential for the application of CP parameters and RCM modes in operational wind retrieval systems. The results of this study provide guidance to direct research objectives once RCM is launched. The results also provide guidance for operational RCM data implementation in Canada’s National SAR winds system, which provides near-real-time wind speed estimates to operational marine forecasters and meteorologists within Environment and Climate Change Canada.

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