scholarly journals Examination of the Daily Cycle Wind Vector Modes of Variability from the Constellation of Microwave Scatterometers and Radiometers

2021 ◽  
Vol 13 (1) ◽  
pp. 141
Author(s):  
Francis Joseph Turk ◽  
Svetla Hristova-Veleva ◽  
Donata Giglio
Keyword(s):  
Microwave Radiometer ◽  
Surface Wind ◽  
Observation Time ◽  
Tropical Pacific ◽  
Convective Precipitation ◽  
Wind Vector ◽  
Tropical Ocean ◽  
Wind Variability ◽  
Diurnal Wind ◽  
The Tropical Pacific

Offshore of many coastal regions, the ocean surface wind varies in speed and direction throughout the day, owing to forcing from land/sea temperature differences and orographic effects. Far offshore, both diurnal and semidiurnal wind vector variability has been noted in the Tropical Atmosphere Ocean-TRIangle Trans-Ocean buoy Network (TAO-TRITON) mooring data in the tropical Pacific Ocean. In this manuscript, the tropical diurnal wind variability is examined with microwave radiometer-derived winds from the Tropical Rainfall Measuring Mission (TRMM) and the Global Precipitation Measurement (GPM), merged with RapidScat and other scatterometer data. Since the relationship between wind speed and its zonal and meridional components is nonlinear, this manuscript describes an observationally based methodology to merge the radiometer and scatterometer-based wind estimates as a function of observation time, to generate a multi-year dataset of diurnal wind variability. Compared to TAO-TRITON mooring array data, the merged satellite-derived wind components fairly well replicate the semidiurnal zonal wind variability over the tropical Pacific but generally show more variability in the meridional wind components. The meridional component agrees with the associated mooring location data in some locations better than others, or it shows no clear dominant diurnal or semidiurnal mode. Similar discrepancies are noted between two forecast model reanalysis products. It is hypothesized that the discrepancies amongst the meridional winds are due to interactions between surface convergence and convective precipitation over tropical ocean basins.

Role of the Atmospheric and Oceanic Circulation in the Tropical Pacific SST Changes

2008 ◽  
Vol 21 (10) ◽  
pp. 2019-2034 ◽  
Author(s):  
Jingzhi Su ◽  
Huijun Wang ◽  
Haijun Yang ◽  
Helge Drange ◽  
Yongqi Gao ◽  
...  
Keyword(s):  
Tropical Pacific ◽  
Hadley Cell ◽  
Convective Precipitation ◽  
Delayed Response ◽  
Positive Temperature ◽  
Subsurface Temperature ◽  
Tropical Ocean ◽  
Temperature Anomalies ◽  
Sst Anomalies ◽  
The Tropical Pacific

Abstract A coupled climate model is used to explore the response of the tropical sea surface temperature (SST) to positive SST anomalies in the global extratropics. The main model results here are consistent with previous numerical studies. In response to prescribed SST anomalies in the extratropics, the tropical SSTs rise rapidly and reach a quasi-equilibrium state within several years, and the tropical subsurface temperatures show a slow response. The annual-mean Hadley cell, as well as the surface trades, are weakened. The weakened trades reduce the poleward Ekman transports in the tropical ocean and, furthermore, lead to anomalous positive convergences of heat transport, which is the main mechanism for maintaining the tropical Pacific SST warming. The process of an extratropical influence on the tropics is related to both the atmospheric and oceanic circulations. The intertropical convergence zone (ITCZ) moves southward and eastward in the Pacific, corresponding to a reduction of the Hadley circulation and Walker circulation. At the same time, convective precipitation anomalies are formed on the boundary of the climatological ITCZ, while the climatological mean convections centered in the Southeast Asia region are suppressed. The largely delayed response of the tropical subsurface temperature cannot be explained only by the strength change of the subtropical cells (STCs), but can be traced back to the slow changing of subsurface temperature in the extratropics. In the extratropical oceans, warming and freshening reduce the surface water density, and the outcropping lines of certain isopycnal layers are moved poleward. This poleward movement of outcropping lines can weaken the positive temperature anomalies, or even lead to negative anomalies, on given isopycnal layers. Displayed on time-dependent isopycnal layers, positive subsurface temperature anomalies are present only in the region after subduction, and are subsequently replaced by negative temperature anomalies in the deep tropics regions. The noticeable features of the density compensation of temperature and salinity indicate that diapycnal processes play an important role in the equatorward transport of the temperature and salinity anomalies from the midlatitude.

scholarly journals Tropical Pacific Surface Wind Energy Spectra and Coherence: Basinwide Observations and Their Observing System Implications

2020 ◽  
Vol 33 (16) ◽  
pp. 7141-7154
Author(s):  
Andrew M. Chiodi ◽  
D. E. Harrison
Keyword(s):  
Surface Wind ◽  
Tropical Pacific ◽  
Central Pacific ◽  
Eastern Equatorial Pacific ◽  
Term Change ◽  
Decadal Scale ◽  
Optimal Spacing ◽  
Minimal Redundancy ◽  
Original Array ◽  
The Tropical Pacific

AbstractThe tropical Pacific moored-buoy array spacing was based on wind coherence scales observed from low-lying islands in the western-central tropical Pacific. Since the array was deployed across the full basin in the mid-1990s, winds from the array have proven critical to accurately monitoring for decadal-scale changes in tropical Pacific winds and identifying spurious trends in wind analysis products used to monitor for long-term change. The array observations have also greatly advanced our ability to diagnostically model (hindcast) and thereby better understand the observed development of central Pacific sea surface temperature anomaly development associated with El Niño and La Niña events, although the eastern equatorial Pacific is not yet accurately hindcast. The original array-design assumptions that the statistics calculated from the western-central Pacific island records are representative of open-ocean conditions and other regions of the tropical Pacific have not been thoroughly reexamined. We revisit these assumptions using the basinwide wind observations provided by the array and find that key wind statistics change across the tropical Pacific basin in ways that could not be determined from the original island wind study. The island results provided a best-case answer for mooring zonal spacing with minimally redundant coherence between adjacent buoys. Buoy-observed meridional coherence scales are longer than determined from the islands. Enhanced zonal sampling east of 140°W and west of 180° is needed to obtain minimal redundancy (optimal spacing). Reduced meridional sampling could still yield minimal redundancy for wind and wind stress fields over the ocean waveguide.

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