SeaWiFS HighlightsJanuary 2003

SeaWiFS Views the Grand Banks

of NewfoundlandGene Feldman (gene.c.feldman@nasa.gov)

NASA GSFC/Earth Sciences Directorate/Laboratory Hydrospheric Processes/SeaWiFS/SIMBIOS Project

The water over the Grand Banks of Newfoundland appears milky green in this image. During the winter, large blooms of phytoplankton are not common, so the cause of this bright patch of water is more likely the resuspension of sediment from the sea floor during the passage of a storm. This assumption is supported by the fact that the southern and eastern edges of the patch roughly mark the edge of the continental shelf where the water becomes too deep for surface wave action to stir the bottom.

The long, linear, east–west oriented clouds visible over the bright water are the contrails of jets which routinely traverse this air space on their way between Europe and North America. POC: 970.2/

SeaWiFS Views the Grand Banksof Newfoundland

January 27, 2003

High Frequency Microwave Radiometer Measurement of Snowfall over Land

AMSU-B 89 GHz AMSU-B 183.3 ± 7 GHz NOAA NWS NEXRAD Data

Case study: Radar reflectivity (dBZ) composite of the March 5-6, 2001 New England blizzard (75 cm of snow deposited on Burlington, VT)

89 GHz channel: Surface effects are evident over the Great Lakes, the St. Lawrence River, and along the Atlantic coast. Cannot distinguish surface from cloud effects.

183.3 ±7 GHz channel: Surface effects are screened by water vapor. Snowfall appears over New England as low brightness temperatures

J. Weinman, G. Skofronick-Jackson, M. J. KimMicrowave Sensors Branch, NASA GSFC

Retrieved Snowfall vs. Radar Observations

These are the first estimates of snowfall rate over land by microwave radiometry.

Snowfall was retrieved by optimizing radiative transfer calculations with respect to measured AMSU-B brightness temperatures.

Retrieved snowfall rate, RNEXRAD reflectivity, Z

Z-R relationships

Provisional comparison between retrieved (red line) and previous snowfall Z-R observations (black lines) shows that:

Snowfall can be retrieved over land using high frequency passive microwave measurements.

More work is needed to improve quantitative retrievals

(mm/h)(dBZ)

Okhotsk Sea P3 Sea Ice AMSR-E Validation

Principal Investigator: J. C. Comiso, Code 971, NASA/GSFC

The P3 underflight mission to the Sea of Okhotsk was successfuly implemented on 7 February 2003. The key objective of this mission is to collect high resolution passive microwave data in conjunction with ship and other satellite observations to validate sea ice parameters derived from AMSR-E in the region and assess the absolute accuracy of these parameters. This study is the first of its kind in the Okhotsk Sea (and therefore unique) since the latter was basically inaccessible to NASA and others during the cold war. The mission was based at the Yokota Air Force Base station in Japan. The aircraft instruments for this mission were the NOAA/Polarimetric Scanning Radiometer (PSR) the GSFC/Microwave Imaging Radiometer (MIR) and the Aircraft Multichannel Microwave Radiometer (AMMR). The P3 was also equipped with the NASA Langley/TAMMS which records temperature and winds in three dimensions as well as navigation. The P3 left the Yokota AF base at exactly 10:00 am. At about the same time of EOS/Aqua overpass over the region, the plane reached the sea ice cover north of the island of Hokkaido. The weather was indeed good and cloud free in the region as predicted and the ship SOYA was positioned along the flight tract to collect in situ data through the efforts of Professor Fumihiko Nishio and Dr. Nakayama of Chiba University. Immediately north of Hokkaido, the ice cover appeared quite complex, being made up of many types and conditions of the ice cover, suggestive of a very active and highly divergent area. Further north, the ice cover became consolidated with only a few leads and a mosaic pattern that covered a rectangular area of 50 km by 150 km was made for an effective statistical comparison with AMSR-E pixels. On the way back to Yokota, the plane went down to 10,000 ft for data collection at an even higher resolution and for a better understanding of the spatial variability of the emissivity of different ice types including new ice.

Comprehensive digital and video photographies were taken at about nadir for direct comparison with PSR data and also from the aircraft window for more general and comprehensive visual characterizations of the ice cover. Envisat ASAR data and Landsat-7 data over the study period were also ordered whenever they are available in the region during the 2-14 February period. We will take advantage of the large spatial coverage of these data for comparative analyses and for AMSR-E validation studies.

Overall, the flight was highly successful. A second flight was scheduled for 11 February but unfortunately, the plane had an altimeter problem and the required part was not expected to be available until 14 February. The second flight would have gone further north to be able reach a prominent and persistent polynya that has been associated with deep ocean convection and to obtain additional data on thick ice and its snow cover. This flight had to be cancelled because the P3 has been scheduled for departure on 15 February for the snow mission in Colorado.

P3/AMSR-E Sea Ice Validation Missionat the Sea of Okhotsk (PI: J. C. Comiso, GSFC/Code 971)

On 7 February 2003, the NASA P3 was flown over the Sea of Okhotsk as part of the EOS-Aqua/AMSR-E validation program for sea ice. The Sea of Okhotsk is the southernmost region with sea ice cover in the northern hemisphere and is vulnerable to climate change. The sea ice cover is also highly coupled with the ocean circulation and productivity of the region. The plan was successfully implemented, with high resolution passive microwave data collected by the PSR, MIR, and AMMR instruments and high resolution satellite data collected with Landsat-7, Envisat ASAR and MODIS. Co-registered visible images were also taken by a digital camera. The mission was coordinated with in situ measurements by a scientific party on board a Japanese ship SOYA. The track of the mission is shown on the right. The P3 was at nominal altitude of 20,000 ft except near the ship on the way back when it went down to 10,000 ft to obtain data at even higher resolution.

Track line for the Sea of Okhotsk Mission.

P3/Polarimetric Scanning Radiometer (PSR)Data at the Sea of Okhotsk

The NASA P3 provided high resolution passive microwave data that can be compared directly with EOS-Aqua AMSR-E and ancillary data. The utility of this data is illustrated in the adjacent images provided by the PSR and digital camera while the P3 was flying over the Japanese ship SOYA which was collecting situ data. Two types of ice are dominant in region: New/thin ice and the snow covered and thicker first year ice as shown in the photographs. First year ice areas, labeled FY, shows high brightness temperatures at low frequencies and low brightness temperatures at high frequencies. The converse is true for new ice. These results are consistent with the scattering and emission properties of the two ice types at different wavelengths as inferred from radiative transfer models. New Ice (NI) Thick FY Ice

(FY)

FY

NI