Data From Weather Satellites

The initial phases of the satellite era (almost for two decades) saw the use of visual imageries provided by the polar orbiting satellites. Towards the end of the seventies the sounders in polar orbiting satellites, the shifting of the US GOES satellite to the Indian latitudes during MONEX experiment and the launch of Japanese GMS satellites provided new avenues. The beginning of eighties saw the INSAT series of the meteorological satellites. The new generation of INSAT satellites to be launched in couple of years from now would have much more atmospheric information over this part of the Asian continent. Besides some experimental satellites such as the Defense meteorological satellite, ERS-1 and satellite like TRMM, are providing valuable information in describing the monsoon features, water vapour , SST, wind and rainfall (Kidder and Vonder Haar, 1995).

Tropical rainfall affects the lives and economies of a majority of the earth's population. Tropical rain systems like hurricane, typhoons and monsoons are crucial to sustaining the live hoods of those living in the tropics. Excess floods can cause drought and crop failure. The TRMM satellite's low inclination (35 degrees), non-sun synchronous, and highly processing orbits allow it to fly over each position on earths surface at different local time. The TRMM has Precipitation radar , TRMM microwave imager(TMI) and visible /infrared scanner.

Now we have launched our own Oceansat-1 onboard IRS-P4 on 26th May, 2003 which contained 8 channel onboard sensor called Ocean colour monitor ( Chlorophyll content ) over ocean and another microwave sensor called Muti-channel microwave radiometer (MSMR) with channel frequencies (6.6 GHz, 10.8Ghz, 18 GHz and 21 GHz) in both horizontal and vertical polarization, and is used to measure geophysical parameter related to ocean such as sea surface temperature (SST), wind speed, total integrated water vapour, and cloud liquid water vapour content (Krishna Rao, 2000).

NOAA satellites have the following meteorological payloads i) Advanced Very High Resolution Radiometer (AVHRR)

ii) TIROS Operational Vertical Sounder (TOVS)

iii) Earth Radiation Budget (ERB)

AVHRR is a five channel scanning radiometer in visible, near infra-red and infra-red wavelengths for analysis of hydrological, oceanographic and meteorological parameters such as vegetation index (i.e. greenness), clouds, snow and ice cover and sea surface temperatures. Data are obtained by all the five channels with a resolution of 1 km. The digital AVHRR data is transmitted from the satellite in real-time (High Resolution Picture Transmission or HRPT) as well as selectively recorded on board the satellite for subsequent playback when the satellite is in communication range of the ground control station. This high resolution data is called Local Area Coverage (LAC). AVHRR data is also sampled on real-time to produce lower resolution Global Area Coverage (GAC) data. The effective resolution of the GAC data is about 4 kms. The spectral characteristics and imaging applications of AVHRR are given in Table 1.

Table 1: Spectral characteristics and applications of AVHRR.

Channel

Spectral Interval (|lm)

Resolution (km)

Application

1

0.58-0.88

1.1

Cloud Mapping

2

0.73-1.0

1.1

Surface water boundaries

3

3.55-3.93

1.1

Thermal mapping, cloud distribution, fire detection

4

10.3-11.3

1.1

Cloud Distribution, SST, WV correction

5

11.5-12.5

1.1

do

TIROS operational vertical sounder (TOVS) incorporates a high resolution infrared radiation sounder (HIRS), a microwave sounding unit (MSU) and a stratospheric sounding unit (SSU). HIRS samples the atmospheric radiation in 20 IR channels and is primarily used to obtain the vertical temperature and moisture distribution in the troposphere. The HIRS uses two carbon dioxide bands for temperature sounding. Seven channels are located in the 15 |m band and six channels are located in the 4.3 |m band. The 4.3 |m channels are added to improve sensitivity (change in radiance for a given change in atmospheric temperature) at relatively warmer temperatures. Moisture is sensed with three channels in the 6.3 |m band of water vapour. The 9.7 |m channel is designed to sense ozone. Three channels are in the atmospheric windows. The 11.1 ^.m and 3.76 ^.m channel is used to detect clouds. SSU samples the radiation from the stratosphere in 3 IR channels. MSU samples the radiation from the atmosphere in 4 channels of microwave region and is particularly useful for obtaining the vertical distribution of temperature in the atmosphere below clouds which are opaque in the infra-red radiation.

Because atmospheric motion is driven by differential absorption of solar radiation and infrared loss to space the study of Earth's radiation budget is extremely important. The latest is the Earth radiation budget experiment (ERBE), which flies on NOAA-9 and NOAA-IO as well as ERBS satellite. The ERBE is designed to make highly accurate (~ 1% ) measurements of incident solar radiation, earth reflected solar radiation, and earth emitted solar radiation at scales ranging from global to 250 km.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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