# Presentation: 518374

## SeaWiFS Views 

**Cyanobacteria in the Baltic Sea**
**Gene Feldman/NASA Goddard Space Flight Center, Laboratory for Hydrospheric Processes, SeaWiFS SIMBIOS Project Office (**_[gene.](mailto:gene.feldman@nasa.gov)__[feldman](mailto:gene.feldman@nasa.gov)__[@](mailto:gene.feldman@nasa.gov)__[nasa](mailto:gene.feldman@nasa.gov)__[.](mailto:gene.feldman@nasa.gov)__[gov](mailto:gene.feldman@nasa.gov)_**)**
- A toxic bloom of the cyanobacteria, *Nodularia spumigena* (more commonly known as blue-green algae), was viewed by SeaWiFS on July 24, 2003, in the Baltic Sea. Located off Sweden's southeastern coast and in the Gulf of Finland, on Finland's southern coast, the algae has bloomed because of high summer temperatures.
- Although not life threatening (according to health officials in Helsinki), the algae can cause a variety of flu-like symptoms if ingested, in addition to burning and itching skin.

## SeaWiFS Views

**Cyanobacteria in the Baltic Sea**

- July 24, 2003

**Notes:**
SeaWiFS Highlights
July 2003
SeaWiFS Views 
Cyanobacteria in the Baltic Sea

A toxic bloom of the cyanobacteria, Nodularia spumigena (more commonly known as blue-green algae), was viewed by SeaWiFS on July 24, 2003 in the Baltic Sea. Located off Sweden's southeastern coast and in the Gulf of Finland on Finland's southern coast, the algae has bloomed because of high summer temperatures. 

Although not life threatening (according to health officials in Helsinki), the algae can cause a variety of flu-like symptoms if ingested, in addition to burning and itching skin.

POC: 970.2/Gene Feldman
gene@seawifs.gsfc.nasa.gov

## East Antarctic Megadunes - ICESat Track 61Christopher Shuman/NASA Goddard Space Flight Center, Laboratory for Hydrospheric Processes, Oceans and Ice Branch (christopher.shuman@nasa.gov)

- Megadunes have a unique morphology and are called "mega" because of their length and breadth rather than their height. The dunes are 2 to 4 meters (6.5 to 13 feet) high, 2 to 5 kilometers (1 to 3 miles) apart, and they can stretch for more than 100 kilometers (62 miles). These features were first noticed by pilots flying over parts of East Antarctica. Observers in the air saw the striped appearance of the long, low dunes. Later, satellite imagery analysis showed that megadunes covered huge areas, totaling approximately 500,000 square kilometers (193,000 square miles).   Megadunes have such subtle slopes that a person on the ground cannot see the pattern and in fact were not noted by early traverses through this area.

- Clearly, the best way to study megadunes in the harsh environment of the high polar plateau is from remote sensing data.  The Terra MODIS mosaic on the left portion of the slide illustrates their general nature and extent.  The ICESat elevation profile on the right side of the slide confirms the earlier remote sensing analysis (Fahnestock et al., 2000) and allows additional analysis of the relationship of these dunes to the nearly constant winds shaping them.  The upwind face is a rough surface of meter-scale sastrugi (or snow ridges, like frozen waves on the ocean) composed of fine snow grains and is bright in the visible imagery.  The downwind side is a smooth surface of icy glaze covering very coarse snow crystals, and is dark in visible imagery except when the viewer is looking towards the sun.  This evidence was gathered during a collaborative field expedition to the area funded, in part, by NSF's Office of Polar Programs.  Dr. Christopher Shuman, Code 971, took part in this project which has completed one field season and is set for another this coming January.

- Antarctica's megadunes are of scientific interest because of their potential impact on climate records being derived from ice cores such as from the nearby Vostok site.  They result from an extreme ice-atmosphere interaction in an area of little to no accumulation.

- East Antarctic Megadunes - ICESat Track 61**Christopher Shuman/NASA Goddard Space Flight Center, Laboratory for Hydrospheric Processes, Oceans and Ice Branch (christopher.shuman@nasa.gov)**

## East Antarctic Megadunes - ICESat Track 61

**Dune topography consistently illustrated by repeat cycles of ICESat tracks (four ascending and four descending tracks intersect near field camp)**
**Amplitudes of several meters and wavelengths of 2-5 km are consistent with the Fahnestock et al. (2000), GRL paper**
**Field data confirms persistent downslope winds that scour/rework the surface and grain recrystalization with low (±0) accumulation**

**Release 11 data via **
**V. Suchdeo**

## Seasonal Trends in Arctic Temperature

-     **Spatially detailed trends in surface temperatures in the Arctic for the different seasons have been quantified for the first time using two decades of AVHRR- IR data. The most positive trends are observed in the summer, while significant trends are also apparent in spring and autumn. Surprisingly, winter data show significant cooling in large regions, especially in northern Asia.  In spring, negative trends are also dominant in much of Greenland.  The trends in spring, summer and autumn are consistent with longer melt period and the observed rapid decrease in the perennial sea ice cover.**

- Reference:  Comiso, J. C. Warming trends in the Arctic J. Climate (in press, 2003). NASA GSFC, Laboratory for Hydrospheric Processes, Oceans and Ice Branch (josefino.c.comiso@nasa.gov)

## Simultaneous Vegetation,

-  Bare Earth, and Bathymetry

- Sand Cut, Florida Keys

**C. Wayne Wright/NASA Wallops Flight Facility, Laboratory for Hydrospheric Processes, **
**Observational Science Branch (Charles.w.wright@nasa.gov)**

## Simultaneous Vegetation,

-  Bare Earth, and Bathymetry

- Sand Cut, Florida Keys

**Notes:**
The photo on the right is of Sand Cut, Elliott Key, Florida.  It is an extremely difficult area to directly survey or monitor due the dense tropical vegetation, insects, rattle snakes, and sharks. It also represents a unique remote sensing challenge because it involves simultaneous sensing of vegetation, bare earth, the water column, and submerged topography.  The Experimental Advanced Airborne Research Lidar (EAARL) is uniquely suited to address mapping and monitoring needs of such environments with it’s water penetrating waveform based laser.  The graphic on the left shows a single scan-line or slice of EAARL data corresponding to the black dotted line across the photo.  The EAARL graphic contains 120 geo-referenced laser return waveforms from vegetation (X axis -120 to –40), bare earth (-40 to –20), the water column and water depth (-20 to 65), and tropical forest (65-100) on the right side.  The EAARL system captures 20 scan-lines each second and produces a comprehensive 3 dimensional dataset plus geo-located digital photographs for the entire flight.

Contact: 
NASA, Code 972, Observational Science Branch
C. Wayne Wright
757-824-1698 Cell: 443-783-3319
Charles.w.wright@nasa.gov

## The MODIS Sea Ice Ice-Surface Temperature (IST) Product

**Dorothy K. Hall*, Jeffrey R. Key**, Kimberly A. Casey+, George A. Riggs+ and Donald J. Cavalieri*****
- *Hydrological Sciences Branch, Code 974, NASA/GSFC, Greenbelt, MD 20771
- **NOAA/NESDIS, 1225 West Dayton St., Madison, WI 53706
- +Science Systems and Applications, Inc., Lanham, MD 20706
- ***Oceans and Ice Branch, Code 971, NASA/GSFC, Greenbelt, MD 20771
- Global sea ice products are produced from the Earth Observing System (EOS) Moderate Resolution Imaging Spectroradiometer (MODIS) on board both the Terra and Aqua satellites.  Daily sea ice extent and ice-surface temperature (IST) products are available at 1-km resolution (**Figure 1**).  Validation activities have been undertaken to assess the accuracy of the MODIS IST product at the South Pole station in Antarctica and in the Arctic Ocean using near-surface air-temperature data from a meteorological station and drifting buoys.  Results from the study areas show that under clear skies, the MODIS ISTs are very close to those of the near-surface air temperatures with a bias of -1.1 and    -1.2oK, and an uncertainty of 1.6 and 1.7oK, respectively (**Figure 2)**.  Uncertainties would be lower if the actual temperature of the ice surface were reported instead of the near-surface air temperature.
- It is not possible to get an accurate IST from MODIS in the presence of even very thin clouds or fog. ** **The clear-sky limitation can possibly be obviated using passive-microwave data in conjunction with MODIS data.  Passive-microwave-derived ice temperatures are not directly comparable with ISTs because the passive-microwave temperature is an integrated measure of the temperature of the upper layers of the sea ice and/or overlying snow cover.  However, if a relationship can be determined between MODIS-derived ISTs and passive-microwave-derived ice temperature, then the passive-microwave derived ice temperatures can be used to approximate IST even through clouds.  Such a product would provide to modelers global IST data daily through cloud cover and darkness though at a coarser resolution than is possible from MODIS if MODIS could be used alone.  With both the AMSR-E and the MODIS on the Aqua satellite it will be possible to assess the relationship between MODIS-derived IST and ice temperature derived from the AMSR-E.
- IST maps are required by energy-balance modelers in order to model heat and salinity fluxes between the ice-covered ocean and the atmosphere.  IST also affects the areal coverage of surface melt, evaporation and sublimation, and the variation in the circulation patterns in the atmosphere and the boundary layer.
- 1-km resolution IST maps derived from MODIS represent the highest-resolution IST product available, globally, on a daily basis.  The MODIS IST product appears to be of comparable or superior quality as compared to predecessor data sets, such as products derived from the AVHRR.  The quality of the MODIS IST maps is such that they are an integral part of a climate-data record following on from AVHRR, and as a predecessor to NPOESS IST measurements, and can be used in long-term climate studies.

## The MODIS Sea Ice Ice-Surface Temperature (IST) Product

**Figure 1**. Terra MODIS ice-surface temperature (IST) product (MOD29) acquired on March 12, 2003 (18:45 UTC), in the northern Greenland Sea in the Arctic Ocean.  The approximate center point of the image is 81.7o N, 1.0o E.  The color scale represents IST in K.

**The MODIS Sea Ice Ice-Surface Temperature (IST) Product**

## The MODIS Sea Ice Ice-Surface Temperature (IST) Product

**Figure 2**.  MODIS IST retrieved temperatures and measured surface temperatures at three locations in the Arctic Ocean on various dates between January 25, 2002, and May 9, 2003.  Most of the measured temperatures were acquired from drifting-buoy data, but a few were acquired from the tide station at Prudhoe Bay, AK.

**The MODIS Sea Ice Ice-Surface Temperature (IST) Product**

## Retrievals of Low Precipitable Water in the Polar Regions from the AMSU-B or SSM/T-2 MeasurementsJames Wang/NASA Goddard Space Flight Center, Laboratory for Hydrospheric Processes, Microwave Sensors Branch (james.r.wang@nasa.gov)

- Retrievals of water vapor profiles or total precipitable water (PW) from microwave radiometric measurements are generally performed over a water surface because the  emissivity is known once the surface temperature is determined. But for low PW  0.8 cm, the AMSU-B (or SSM/T-2) channels near 183 GHz could be used to retrieve PW over any surface as demonstrated for the polar regions shown in the figure.
- The retrieval accuracy, without corrections for surface temperature and emissivity variations, could be as much as ±0.1 cm.  When corrections for these surface variations are made the retrieval accuracy is excellent, generally on the order of ±0.03 cm.
- Although the PW is generally small in these regions it remains the most important greenhouse gas and plays a crucial role in the mass balance of the ice sheets and their corresponding effects on global sea level.
- When PW is known the surface emissivities over a wide frequency range (up to 150 GHz) can be determined if the surface temperature is also measured.  This potentially gives a more complete and better description of the physical properties of sea ice and/or snow cover, and thus provides more reliable retrievals of these parameters.

## AMSU-B Retrieved Total Precipitable Water in the Polar Regions

- Arctic Region, January 15, 2003

- Antarctica Region, July 1, 2003

**AMSU-B Retrieved Total Precipitable Water in the Polar Regions**