Hiroto Abe

Evaluation of sea surface salinity observed by Aquarius and SMOS

Sea surface salinity data derived from Aquarius and Soil Moisture and Ocean Salinity (SMOS) missions were compared with observations by Argo floats in the global oceans and outputs from a global ocean data assimilation system to evaluate the quality of the salinity measurements and assess the error structure in the data. Under the condition of sea surface temperature (SST) higher than 5°C and wind speed lower than 15 ms-1, salinity observed by Aquarius agreed well with the Argo data with an rms difference of 0.6 psu. If we applied spatial and temporal averages over 1° × 1° and one month, the rms difference was reduced to 0.3 psu. The residual of the salinity observation depended significantly on the SST and wind speed, as expected from the principle of salinity measurement. Also bias caused by inaccurate corrections for the galactic radiation and radio frequency interference were considered to contribute largely to differences with in-situ observations.

Evaluation of sea surface salinity observed by Aquarius

Sea surface salinity data derived from Aquarius and Soil Moisture and Ocean Salinity (SMOS) missions were compared with observations by Argo floats in the global oceans and outputs from a global ocean data assimilation system to evaluate the quality of the salinity measurements and assess the error structure in the data. Under the condition of sea surface temperature (SST) higher than 5°C and wind speed lower than 15 ms-1, salinity observed by Aquarius agreed well with the Argo data with an rms difference of 0.6 psu. If we applied spatial and temporal averages over 1° × 1° and one month, the rms difference was reduced to 0.3 psu. The residual of the salinity observation depended significantly on the SST and wind speed, as expected from the principle of salinity measurement. Also bias caused by inaccurate corrections for the galactic radiation and radio frequency interference were considered to contribute largely to differences with in-situ observations.

Oceanic Rossby Waves over Eastern Tropical Pacific of Both Hemispheres Forced by Anomalous Surface Winds after Mature Phase of ENSO

AbstractThe present study examined ENSO-related wind forcing contribution to off-equatorial Rossby wave formations in the eastern tropical regions of the North and South Pacific using satellite altimeter data and atmospheric reanalysis data during the period of 1993–2013. After mature phases of ENSO events, the sea surface height anomaly fields showed that off-equatorial Rossby waves propagated westward along 11°N and 8°S from the eastern Pacific. Starting longitudes of the westward propagation were distant from the eastern coast, especially for weak El Nino events in the 2000s, in contrast to the strong 1997/98 El Nino event in which the propagations started from the coast. Based on observational data, it was hypothesized that the Rossby waves could be formed by off-equatorial zonal belts of wind stress curl anomalies (WSCAs) in 135°–90°W rather than by wave emissions from the eastern coast. A numerical model forced only by WSCAs, that is, without wave emissions from the coast, successfully reproduced ob...

Evaluation of sea surface salinity observed by Aquarius on SAC-D

A passive and active L-band microwave sensor, Aquarius, developed by NASA to observe the global sea surface salinity (SSS) distribution, was launched on 10 June 2011. The SSS observed by Aquarius (v.1.3) was evaluated by comparison with in-situ salinity data from various sources. The Aquarius SSS generally agreed well with salinity measurements by Argo floats in moderate to high sea surface temperature (SST) regions. However, the Aquarius SSS highly deviated in low SST and high wind regions. Typical root-mean-squared difference between the Aquarius and in situ SSS observations under a condition of sea surface temperature higher than 5°C were 0.7 psu for snapshot observations and 0.35~0.4 psu for monthly 1° x 1° averages.