Observation forms the basis of research in Atmospheric and Environmental Science. The success of ASP and IGBP depends on data from a reliable and adequate set of instruments. The number of weather observatories in NER was too less to have enough data to conduct a meaningful study on weather and climate. NESAC with support from ISRO took necessary steps to reduce the gaps in such observational network. ISRO developed Automatic Weather Station (AWS) came handy in this initiative. The centre has also procured instruments to study the physical properties of aerosols and its forcings, planetary boundary layer, upper atmosphere, etc.
Automatic Weather Station Network
Eighty AWS have been installed across eight states of NER in collaboration with several state and central government institutes operating in the region. The AWS records hourly data on Rainfall, Wind Speed, Wind Direction, Atmospheric Pressure, Relative Humidity, Temperature and Sun shine duration. The data is stored in a local data logger in addition to transmitting twice within one hour after collecting the data. The transmitted data is received at meteorological and oceanographic satellite data archival centre (MOSDAC), Space Applications Centre, Ahmedabad and put in their web site (http://mosdac.gov.in). There are 24 AWS in Assam, 16 in Meghalaya, 15 in Arunachal Pradesh, 7 in Nagaland, 6 in Manipur, 5 in Mizoram, 5 in Tripura, and 2 in Sikkim.
The data from these AWS are being extensively used by Agriculture departments, water resource departments, etc. of some state governments. Besides, the data forms back bone of flood forecasting and drought estimates, being carried out by NESAC.
Mini Boundary Layer Mast
It provides wind speed, wind direction, temperature and relative humidity at three vertical levels (at 8m, 8m and 15m). In addition it provides ground level data on rainfall, atmospheric pressure, net incoming and outgoing radiation, soil moisture (at five levels up to 1 m) and soil temperature (at seven levels up to 1m). It can record data at 1 second interval and transmits every four minutes average data via SMS using a GSM connection.
Sound Detection and Ranging (SODAR)
The data from this instrument is used for studying the boundary layer dynamics. It provides the wind speed value along the E-W, N-S and vertical direction and measures the pockets of turbulence within the atmospheric boundary layer. The instrument provides vertical profile data up to 1 km (apprx.)
Atmosphere probing using Pisharoty sonde
Pisharoty sonde along with the ground station hardware were developed by VSSC, Thiruvanthapuram. One sonde is launched every week using hydrogen gas filled balloon. The sonde has sensors for measuring ambient temperature, relative humidity, atmospheric pressure and a GPS receiver and a transmitter. The GPS receiver estimates the instantaneous position of the balloon which is used to find the wind speed and direction. The sonde collects and transmits data at one second interval. The balloon normally reaches to a height of 25 km (apprx) before burst.
Multi Wavelength Radiometer
The instrument was developed by Space Physics Laboratory, Thiruvanandapuram. It records Aerosol optical depth, columnar water vapor and columnar ozone, by measuring spectral extinction at ten wavelength bands, centered at 380, 400, 450, 500, 600, 650, 750, 850, 935 and 1025 nm.
Microtops II Sunphotometer
The instrument records Aerosol optical depth, columnar water vapour and columnar ozone by measuring spectral extinction at five wavelength bands, centered at 380, 440, 500, 936 and 1020 nm. It is a light weight and portable instruments, ideal for field measurements. It has a GPS receiver connected to it to record the measurement location.
The instrument provides aerosol black carbon (BC) concentration in ng per m-3 of air sample at seven different channels (wavelength centered at 370, 470, 520, 590, 660, 880 and 950 nm). Aerosol BC is a very critical particulate pollutant having strong radiation absorbing characteristics. The spectral measurement of BC helps in understanding the potential BC sources and their relative impact.
The instrument measures aerosol light scattering / extinction coefficient in terms of total scattering coefficient and back scattering coefficient. The measurement is done at three wavelengths corresponding to Blue (450 nm), Green (550 nm) and Red (700 nm) color with 40 nm band width. The Nephelometer is a photon counting instrument. Particles and gas molecules scatter photons that are detected and counted using highly sensitive PMT tubes. These photon counts are converted into counting frequencies and correlated to light scattering coefficients using calibration constants.
The instrument measures drop size distribution (DSD) of rainfall reaching at ground. The rain drops are classified into 20 classes based on drop diameter (below 0.3 mm, more than 5.3 mm and 18 classes between 0.3 to 5.3 mm). It provides total rain, rain drop number density (per m-3of air), total precipitable water etc. The sampling time is user selectable and at NESAC the data is collected at every 30 seconds.
Micro Rain Radar
It is FM-CW (frequency modulated continuous wave) radar operating at 24.1 GHz. It measures the vertical profile of DSD of rainfall. The profile is measured at 32 range gates and at every level total rain, rain drop number density (per m-3of air), total precipitable water etc are measured. The range bin (200 meter at NESAC) and sample interval (30 seconds at NESAC) is user selectable.
The centre is also procuring Electric Low Pressure Impactor, Boundary Layer Lidar (BLL), and Online analysers for SOx, NOx, CO, CH4,O3 gases.