Passive microwave measurements from the AMSR-E instrument on NASA’s Aqua satellite are used to estimate in precipitation associated with weather systems outside the range of land-based radars. In the image above, AMSR-E produces a radar-time analysis of rain associated with Hurricane Katia. Note the intense convective storms just north of Puerto Rico. Could this be another storm developing?
Archive for the ‘AMSR-E’ Category
As T.S. Lee strengthens just off the Gulf Coast, the NASA instruments on the Aqua satellite capture dramatic images of the storm. The color enhanced infrared image from MODIS shows the regions of the coldest cloud tops in the storm where the rainfall is likely to be most intense. The companion image from AMSR-E at the same time shows the observed instantaneous rainfall from the storm. This rainfall information is particularly valuable to local forecasters to identify regions for flood and flooding potential, especially from portions of the storm outside land-based radars.
AMSR-E precipitation estimates give forecasters additional information on storm intensity. Note the differences in rain location in the AMSR-E image above and the cold cloud top temperatures in the MODIS infrared image below. Both of these Aqua instruments captured storm information simultaneously while orbiting over Irene early in the afternoon on August 26, 2011.
The AMSR-E instrument on the NASA Aqua satellite provides an instantaneous rain rate product. Outside of radar range, Tropical Storm Don is seen by AMSR-E. Note there is a large area of 1 in/hr rainfall occurring with maximum rates near 1.5 in/hr in a few pixels. While this data is not available as quickly as radar data, it may provide valuable information in radar void areas of the Gulf of Mexico, the Southwest or in areas between radars where rainfall estimates may be less accurate. In flash flooding situations, the AMSR-E data can be compared to radar estimates as little as 2 hours after the event (NASA/LANCE). If large differences are seen, one may determine if further actions are warranted due to the affects of more or less rainfall on the flooding situation.
The 19 May SPoRT run of the Weather Research and Forecasting (WRF) model captured a band of strong convection that developed in advance of a dryline across Kansas and Oklahoma. The mode and orientation of the convection appeared quite similar to the observed radar reflectivity in the late afternoon and evening hours. On the multi-model comparison page as part of the 2011 Hazardous Weather Testbed’s Spring Experiment, the SPoRT-WRF model is compared to the National Severe Storms Laboratory (NSSL) and the National Center for Atmospheric Research (NCAR) WRF runs. For this particular day, the SPoRT-WRF best captured the intensity and timing of the convection over Oklahoma and parts of Kansas during the late afternoon and evening hours (see Figure below of reflectivity comparisons valid at 0000 UTC 20 May 2011). The SPoRT WRF model configuration is nearly identical to the NSSL configuration, but incorporates real-time MODIS vegetation fraction, high-resolution land surface initialization data from the NASA Land Information System, MODIS/AMSR-E SSTs, and also assimilates AIRS temperature and moisture profiles to improve initial conditions and subsequent forecast parameters. Of course, this is only one case; SPoRT team members plan to continue examining the model comparisons throughout the duration of the Spring Experiment and beyond.
Recently the Mobile WFO has begun ingesting the new MODIS Enhanced SST composite. Steve Miller and Ray Ball of WFO MOB worked with SPoRT to set up this capability in AWIPS/D2d. Below is an example of their display of the data matching the SPoRT web graphics color scheme.
This post is a follow-on to both GaryJ’s comments on this morning’s LIS snow water equivalent (SWE) post, and to the post on MODIS snow cover mapping. I went ahead and produced a LIS SWE graphic at 1900 UTC 31 JAN 2010, approximately coincident to the time of the MODIS false color snow map (1919 UTC) and geographical area.
The image below shows the output from the 3-km SPoRT LIS that could be used to help quantify the actual water content of the snow cover. Compared to the MODIS false color image in the previous post, it appears that the LIS-Noah SWE coverage may be slightly overdone on the southern edge of the swath from Arkansas to Georgia. This is probably due to the fact that the Noah land surface model running within LIS adds to the SWE field anytime the land surface temperature is below freezing. Therefore, areas of mixed precipitation or freezing rain also lead to an accumulation of the SWE field.
A unique product that may be worth considering is to supplement the MODIS snow mask with quantitative information from LIS within the mask indicated by MODIS. Another option may be to assimilate AMSR-E SWE information to help adjust the LIS SWE field towards the satellite observations.
SPoRT is preparing a high resolution water temperature product for the Great Lakes region as subset of the enhanced MODIS/AMSR-E SST composite (beta version released last month). The example below shows significant detail in the surface water temperature structure across sections of each lake. Forecasters use this information in a diagnostic mode and prognostically (in weather forecast models) to improve the prediction of clouds and precipitation in the Great Lakes region. This will have significant impact in Lake effect snow situations.
The product will be available for use in the WRF EMS v3 and in AWIPS early next year.
Hurricane Ida (now a tropical storm) was located in the eastern Gulf of Mexico at 0745 UTC on November 11, 2009. A descending orbit of the NASA A-Train observed the tropical cyclone. Here, rain rates estimated from the passive microwave data of AMSR-E are shown (inset), with widespread heavy rains located throughout the northern half of the circulation center. Further north, estimated precipitation rates decreased with distance from the strongest convection. Passive microwave brightness temperatures and retrieved rain rates provide additional detail over the traditional infrared appearance, where the structure of the cyclone rain bands is masked by dense cirrus overhead.
In addition to the AMSR-E aboard Aqua, the CloudSat radar passed just to the west of the circulation center. Radar reflectivity indicates a steady decrease in (detectable) cloud top height moving from 25 to 28N latitude, or decrease in cloud top altitude with distance from the circulation center. Neither the AMSR-E or infrared data are able to depict the 5 km variability in cloud top height. The radar also provides value by highlighting the presence of individual convective cores, where reflectivity is likely enhanced by the presence of graupel. Near the 4-5 km level, the thin band of enhanced reflectivity suggests the presence of the melting level. This feature does not seem to appear underneath the higher cloud tops at 25 N, however, the disappearance is likely a result of attenuation of the radar signal through the deeper convective cores. The CloudSat signal is best suited for small particles and ice, and attenuates rapidly in heavy liquid precipitation. Therefore, returns are limited below the melting level, given the high rain rates suggested by AMSR-E data.
The multiple, yet nearly simultaneous perspectives provided by the A-Train allow for a more complete depiction of precipitation structures, especially for storms that are offshore and out of the range of ground based radars.
The AMSR-E images shown are of rain rate and sea surface temperature as Hurricane Bill headed north alongside the U.S. east coast. Note the capture of the cooler SST in the wake of Bill on the order of 5-10 degrees Fahrenheit. Also, note the rain structure and intensity of the storm at this time seen in the rain rate image.