Analysis of densely observed TRMM/PR data during 180-degree yaw maneuver

The Tropical Rainfall Measuring Mission (TRMM) satellite performs 180-degree yaw maneuver (yaw-around) when the solar beta angle which is the angle between the satellite orbit plane and the direction to the sun crosses the 0-degree. The yaw- maneuver is completed about 16 minutes (about 7000 km in flight length on the Earth) in the TRMM case. During the yaw-around, the precipitation radar (PR) onboard TRMM continues nominal observation (but data processing is limited to level-1 algorithms). Therefore very dense observation is realized during the yaw- around. Since nearly fixed target (rain echo and surface echo) is observed by different incident angles in a short time, new information can be obtained that cannot be obtained nominal observation. On the incident angle dependency of the sea surface echo, we can avoid the uncertainties comes from the changes in the target. Range profiles of the sea surface echo of different incident angles are compared with the long-term global average data. The same approach can be used to quantitative estimation of bright band structure such as blurring effect of the off-nadir incident angles. A case study on 24 January, 2000, which is the stratiform rainfall case over Borneo Island and the range of the incident angle is about +/- 6 degrees, shows that significant difference cannot be seen among data and that the echo strength of each height concentrate within 3-dB. However, the range profiles of the surface echo underneath the stratiform rainfall show quite different angle bin dependency from the reference echo profiles near the rain area. For convective echoes, the nonuniform beam filling (NUBF) effect can be estimated by the different incident angle data and the data which location is slightly offset from the center. More reliable path integrated attenuation (PIA) can be obtained from different incident angle data and the NUBF can be estimated both by the range profiles of surface echo of off-nadir angle bin data with an approach b- y Takahashi et al. (2006) and their change with the location within a footprint.