A. K. De

Bio: A. K. De is an academic researcher from Indian Statistical Institute. The author has contributed to research in topics: Rain gauge & Cloud height. The author has an hindex of 2, co-authored 3 publications receiving 19 citations.

Cloud Height, Cloud Temperature and Cloud Attenuation in Microwave and Millimeterwave Frequency Bands over Indian Tropical East Coast

Abstract: Based on radar RHI (Range height indicator) measurements, cloud height has been deduced during the worst months (July–August) over Kolkata. Such cloud height results have been utilized to estimate cloud temperature. The attenuation of radiowave due to cloud in various probability levels has been determined in millimeter wave and microwave frequency bands. Such results on different probability levels are useful for satellite communication and remote sensing application over the aforesaid station in tropical India.

Yearly variability of rain attenuation over a communication link at 13 GHz during monsoon months over Indian eastern region

Abstract: In this paper, results on yearly variability of measured attenuation at 13 GHz under rainy conditions over a microwave communication link path situated between Sarojini College and Airport of Dum Dum area in Kolkata have been presented. The link belongs to an user agency and suffers a large attenuation due to heavy rain. The variation microwave amplitude was monitored and rain rate measurements were made on regular basis simultaneously by a fast response rain gauge in the monsoon months during 2007 and 2008. The observed microwave radio signal was characterized with a steady signal level ~−42 to −43 dBm with fade depth ~1 to 2 dB under clear sky situation. The results on attenuation have been studied in relation to simultaneous rain rate measurements. Yearly variability of rain attenuation has also been highlighted. These results are also useful for designing and installation of future microwave communication links both for terrestrial and satellite paths in this part of India, where rain characteristics are similar to Indian eastern coastal station. The probability distribution of attenuation and rain rates has been deduced from measured observations.

Non performance estimation of a microwave communication link due to rain during the monsoon months of 2006 over Kolkata

Abstract: The non performance of a microwave communication link located over Kolkata due to heavy rain in the monsoon months of 2006 has been investigated by monitoring the amplitude variation of signal on twenty hour basis. It has been seen that the link did not serve any purpose for 4% during the monsoon period of 2006 while the signal level was less than −78 dBm. Infact the study revealed that the link performance started deteriorating when the signal was of the order of −73 dBm.

Analysis and improvements of cloud models for propagation studies

Abstract: [1] Two cloud models currently in use in propagation and remote sensing simulations in the presence of nonprecipitating clouds were analyzed. A new cloud model is also proposed: a modification of a humidity threshold to better identify clouds is suggested, as is a new cloud density function for computing cloud liquid and ice content within a cloud. The performances of the threshold functions were examined at the Atmospheric Radiation Measurement (ARM) Program's Southern Great Plaints (SGP) site in Oklahoma, USA, by using radiosonde and ceilometer data. The new threshold showed an improvement in the cloud detection (15%) and a reduction of false cloud identification in clear-sky conditions (26%). Next, the cloud density models were evaluated in the brightness temperature (Tb) domain, by comparing simulated Tb values in cloudy conditions with those measured by dual-channel microwave radiometers at several ARM sites. The new model provided good results in comparison with the radiometer measurements, with overall root mean square (RMS) differences of 3.10 K, reducing the RMS by about 16% with respect to the best of the other models. Improvements can be noticed in particular at SGP (20%), and in the tropics (37%).

Cloud Liquid Water Content and Cloud Attenuation Studies with Radiosonde Data at a Tropical Location

Abstract: The profile of cloud liquid water density and the total liquid water content (LWC) are obtained from the radiosonde data using the Salonen model at Kolkata, India, a tropical location. The cumulative distribution LWC shows a departure from the ITU-R model at this location, exhibiting a significantly enhanced occurrence during the monsoon months. The cloud attenuation, derived by integrating the profile of specific attenuation obtained from the radiosonde data, is related to LWC at different frequencies in the range 10-100 GHz. A comparison indicates that the cloud attenuation at frequencies below 50 GHz is somewhat overestimated by the ITU-R model generated values and significantly underestimated by the ITU-R model at frequencies above 70 GHz at the present location.

Cloud Attenuation for Satellite Applications Over Equatorial Climate

Abstract: A propagation experiment has been carried out at Penang using the SUPERBIRD-C satellite beacon. Cloud occurrences were observed during different months and it is seen that the low cloud occurrences over Penang is very significant from October to January. The cloud attenuation results that are presented, which include the testing of models, have been obtained from the data gathered over five years.

Cloud attenuation and cloud noise temperature over some Indian eastern stations for satellite communication

Abstract: In this paper, cloud characteristics in relation to radio wave propagation over some selected locations in different geographical region in eastern India have been presented. It is seen that low cloud occurrence over Patna, Bhubaneswar and Ranchi is quite significant. The performance of radio systems deteriorates due to cloud attenuation as well as due to cloud noise temperature. Based on the cloud attenuation results, the total atmospheric noise temperature including the noise contribution from cloud for different months during different times for different cloud thicknesses at 10 GHz, 18 GHz, 32 GHz, 44 GHz and 70 GHz has been determined for the aforesaid stations. The results, presented here are useful to design future earthspace communication links over these aforesaid locations in India.

Cloud-Cover Statistics and Cloud Attenuation at Ka- and V-Bands for Satellite Systems Design in Tropical Wet Climate

Abstract: Cloud-cover statistics, low cloud base height, frequency of precipitation, 0°C isothermal height, and integrated cloud liquid water and cloud attenuation have been obtained for the tropical rain forest climatic zone of Africa. The cumulative distribution of integrated cloud liquid water content shows a departure from the ITU-R model. A comparison of cloud attenuation at Ka-and V-bands show that the ITU-R model underestimates the attenuation up to about 1.7 and 2.3 dB at 30 and 50 GHz, respectively.