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rajeevan _at_ narl.gov.in
NARL is starting a modeling research group with the following objectives:
One of the major thrust is to assimilate meteorological data being acquired by the Department of Space (DOS) network, which includes AWSs, MST radar, Lidar and GPS sonde. It is also proposed to acquire Dopplar radar data (from India Meteorological Department) and Radio Occultation profiles to assimilate into models. This assimilation will be made on daily basis for operational forecasts as well as for some specific case studies to examine the impact of data assimilation.
The modeling group also will be working on improvement of physical parameterization schemes by validating using data from the experimental campaigns. The MU radar data and EAR at Indonesia may be also useful for this work.
pslu _at_ narl.gov.in
Brief experimental proposals:
Proposal-1: wish to study the discrete atmospheric targets like precipitation, convection, lightning, meteors using multi-channel receive radar (MU). It is proposed to apply radar interferometry/imaging techniques to image the evolution of the above events. It is proposed to work with a broad transmit beam (20-deg) by phasing the array appropriately.
Proposal-2: wish to compare the results (winds) obtained with atmospheric radar techniques such as DBS, SA, and "successive pattern moving" approach. This is possible with MU radar where multiple receivers are employed.
Proposal-3: wish to study/track the space debris using MU radar using mono-pulse tracking and other techniques.
Proposal-4: I am involved in the design of atmospheric radars in UHF/VHF/HF/ MF bands. We are utilizing the solid-state TR modules and multi-channel digital receivers. The monitoring of TR modules during the operational life period is very important. Since RISH is operating MUR, LTR and EAR, which are very modern in nature, I wish to have technical collaboration with RISH on the following specific areas
tvcsarma _at_ narl.gov.in
Development of RASS for MST radar under collaboration with RISH has progressed well. Presently work is progressing on solving outstanding problems of discontinuous coverage in height and time. Extension of this technique for wind profilers in VHF and UHF bands is planned.
akpatra _at_ narl.gov.in
Ongoing collaborative research programs:
At present, I am carrying out two research projects using the EAR and collocated experiment in collaboration with RISH, Kyoto University; STEL, Nagoya University; and NICT. These two projects are meant to investigate (1) daytime 150-km echoing phenomenon and (2) dynamics, electrodynamics and plasma instabilities associated with low latitude QP echoes. In addition, an exploratory type experiment to search for daytime 150-km echoes using the MU radar was conducted in June 2008.
Our investigations on 150-km echoing phenomenon using the EAR have made significant impact in furthering the development of theory. If we succeed in detecting these echoes using the MU radar (which we need to examine carefully now), these efforts are going to be revolutionary in understanding the physical processes that have been puzzling researchers for more than 40 years.
Proposed future research activities:
kraghunath _at_ narl.gov.in
Involved in the lidar Design Development and presently working on realizing a Rayleigh Doppler lidar for measuring middle atmosphere winds. There is a plan to operate Rayleigh and Sodium lidars in near simultaneous modes and to extend Rayleigh operations during day time.
Interested to involve/collaborate in key lidar technology areas (like high spectral resolution measurements) pursued/pursuing at RISH
ypbk _at_ narl.gov.in
Proposed collaborative activity with RISH, Japan for development of Raman lidar system for meteorological applications
National Atmospheric Research Laboratory (NARL), Gadanki is developing a portable lidar system for profiling the atmospheric water vapour and also atmospheric temperatures in the height region covering the lower troposphere. For this rotational-vibrational Raman technique is proposed for the atmospheric water vapour measurements and the pure rotational Raman technique is proposed for the atmospheric temperature measurements. The lidar system will make use of 2W class 355 nm laser and employs 350 mm aperture telescope. The proposed lidar system will also be used for aerosol research in characterizing the lidar ratio from Raman and Elastic backscatter profiles. The proposed system is planned for initially in nocturnal periods of observation.
It is proposed to have scientific and technical collaboration with RISH, Japan in development of the above system.
trp1910 _at_ narl.gov.in
tnrao _at_ narl.gov.in
Why convection is weak over Kototabang?
The Equatorial Atmospheric Radar (EAR) is located in a convectively active region of western Pacific. The moist static energy available for the development of deep convection is large in those areas, and are of the order of 1000-2000 J kg-1 (Kingsmill and Houze, 1999; McBride and Frank, 1999). If this energy converts into kinetic energy (in ideal case), the resulting updrafts should be of the order of few 10s of m s-1. However, the published literature (on convection, gravity waves generated by convection) shows very weak vertical velocities even in deep convection (Dhaka et al., 2006). They have reported that the magnitude of vertical air velocity during convection over Gadanki (another tropical station) was larger by a factor of 3 in comparison to those over Kototabang. Further, the convection is also not deep over Kototabang (as informed by Prof. Tsuda during the discussion at NARL). If the convection top (or level of neutral buoyancy) is not reaching higher altitudes, then the total moist energy should result into large vertical velocities (and also positive thermal buoyancy should be large). What could be the reason for the shallow and weak convection over Kototabang? Is it due to the spatial variability? In other words, the moist energies reported earlier do not really represent for the Kototabang region? Are processes like, water loading and entrainment of ambient air into the cloud are dominant over this region? Note that the above processes reduce the positive thermal buoyancy and thereby weakens the updrafts. Or the observed weak velocities are simply because of excessive incoherent averaging?
Small scale processes near the mid latitude tropopause:
The exchange across the extratropical tropopause depends mainly on small-scale near-tropopause processes, such as tropopause folds, cutoff lows, streamers, etc. Traditionally tropopause folds are believed to be the major agents for STE. Sprenger et al. [2003], however, argued that the tropopause folds account only for 10-30% of all STE events in the extratropics and other processes like breakup of stratospheric streamers and erosion of cutoff lows are equally important for STE. Nevertheless, the exchange in other processes generally confine to the upper-middle troposphere. The folds, on the other hand, are deep intrusions and can reach to lower tropospheric altitudes. The exchange occurring at these heights (mid and lower troposphere) as a result of turbulent mixing thus has a large impact on the tropospheric chemical budget. Tropopause folds have been monitored and studied for a long time by means of in situ aircraft measurements and remote sensing techniques, including air-borne and ground based laser systems and radars (Rao et al., 2003; Rao and Kirkwood, 2005 and references therein). The advantage in using the remote sensing instruments is that they provide tracer information with good height and temporal resolution, which can be extremely useful in studying the time evolution of the fold. The added advantage with VHF profilers is that they readily provide turbulence information. This information can be used to estimate the ozone flux across the boundaries of the fold (Rao et al. 2005). Recently Rao et al. (2008) used continuous measurements of ESRAD to build the climatology of tropopause folds over Esrange, a station within the polar circle. Using Middle and Upper (MU) radar at Shigaraki, the structure and characteristics of mid latitude folds can be studied, in detail. It is believed that the fold will have several thin and laminar layers within the folded structure. These thin and stable layers of enhanced ozone (and low humidity) will increase the surface area for mixing with the free troposphere. The MU radar can be operated in frequency domain interferrometry to better understand these layers. If simultaneously, information of some stratospheric tracers (such as ozone) is available, then the importance of these layers in enhancing the ozone flux can be brought out in a better way.
vratnam _at_ narl.gov.in
Working in the area of Middle Atmospheric Dynamics using both ground-based and space-borne measurements. Particularly concentrating on GPS RO related studies including validation, global variation of atmospheric boundary layer height, global distribution of water vapor, tropical tropopause characteristics, characteristics of Indian Summer Monsoon, gravity and planetary wave studies.
Since our missions (ROSA on Oceansat-2 and Megha Tropiques) are coming up we are interested in developing our own retrieval algorithms besides validation and scientific utilization of GPS RO data. We would like to get support from RISH in the following three areas:
1. Validation of GPS RO: We have detailed plan for validation of ROSA onboard Oceansat-2 over Indian region. We would like to get original records of high resolution GPS radiosonde over Japan and Indonesian region where RISH has strong hold. 2. Parameter retrieval for GPS RO: Since the RISH is one of the experts in data retrieval of GPS RO we would like to get help in retrieving the GPS RO final products. 3. SAFAR campaign: We are running a major campaign, SAFAR (Study of Atmospheric Forcing And Responses), using coordinated facilities available at NARL. In near future it planned to extend to Indonesian and Japan region where coordinated facilities are available to study the latitudinal variation.
SuSridharan _at_ narl.gov.in
Long-term Variability of Middle Atmospheric Winds and Temperature over Low-latitudes
The horizontal wind data acquired by MF radar at Tirunelveli (8.7 N, 77.8 E) are used to study long-term variability of mesosphere and lower thermosphere (MLT) winds. The annual mean meridional winds over Tirunelveli show monotonic change from northward to southward from the year 1993 to 2006 (Sridharan et al. 2007). This result is in contrast the results reported from mid-latitude where decreasing trend in the annual mean southward winds was noted (Bremer at al., 1997; Jacobi et al., 2001). The long-term trends in the middle atmospheric temperature (March 1998-March 2008) derived from Rayleigh backscattered signals received by the Nd:YAG lidar system at Gadanki (13.5?N, 79.2?E) are investigated. The altitude profile of trend coefficients estimated from the ten years of temperature observations show that there exists cooling at the rate of 0.12}0.1 K/year in the lower stratospheric altitudes (35-42 km) and 0.2}0.08 K/year at altitudes near 55-60 km. The trend is nearly zero (no significant cooling or warming) at altitudes 40-55 km.
Solar cycle, cooling of the middle atmosphere owing to increase of CO2 and/or decrease of O3, and other effects may be suspected as cause of the long-term trends in winds and temperature. As the mean meridional circulation at mesospheric altitudes is driven by gravity waves, the long-term variabilities of gravity waves need to be examined at different altitude regions at and below the mesospheric heights over low and mid-latitudes. Through GPS temperature measurements in the troposphere and stratosphere, global climatologies of gravity/planetary waves can be obtained (Tsuda et al., 2000). Combined lidar and MF/meteor radar measurements in India, Indonesia and Japan can be collectively used to obtain long-term gravity wave climatology in the troposphere, stratosphere and mesosphere to understand the trends in middle atmospheric winds and temperature.
References: Bremer J., R. Schminder, K.M. Greisiger, P. Hoffmann, D. Kurschner, W. Singer, 1997: Solar cycle dependence and long-term trends in the wind field of the mesosphere/lower thermosphere. J. Atmos. Solar-Terr. Phys. 59, 497-509. Jacobi, CH., M. Lange, D. Kurschner, A.H. Manson, C.E. Meek, 2001: A long-term comparison of Saskatoon MF radar and Collm LF D1 mesosphere-lower thermosphere wind measurements. Phys. Chem. Earth 26, 419-424. Tsuda, T., M. Nishida, C. Rocken, R.H. Ware, 2000: A global morphology of gravity waves by GPS/MET data. J. Geophys. Res. 105, 7252-7273.
S. Sridharan, T. Tsuda, and S. Gurubaran, 2007:Radar observations of long-term variability of mesosphere and lower thermosphere winds over Tirunelveli (8.7?N, 77.8?E), J. Geophys. Res., 112, D23105, doi:10.1029/2007JD008669, 2007.
taori _at_ narl.gov.in
Airglow Research at NARL
NARL is establishing aeronomy experiments and at present we are developing a narrow-band mesosphere lower thermosphere photometer that operates at OH, O2, O(1S) and O(1D) emission wavelengths. Together, installed at NARL is university of western Ontario scanning radiometer that operates at OH wavelengths with which mapping of short horizontal wavelength is planned. We look for a possibility of installing an imager that could operate at OH and O(1D) wavelengths simultaneously so that a comprehensive suit of optical instruments can be operated that would provide mesospheric temperatures together with imaging of short and long period wavelengths.
ndashora _at_ narl.gov.in
As per the discussion in the meeting, I wish to put the research plans in brief as follows: My research work belong to 1. Study the effects of Space Weather events/Geomagnetic storms on equatorial and low-latitude ionospheric electrodynamics and hence on electron density variations. (SPACE Physics Part of RISH) 2. Study the day to day variability of ionospheric irregularities related to Equatorial Spread F and effect of Space Weather events on it. (Radio Science Part of RISH) I am well versed with ground based GPS receiver techniques for studying the ionospheric total electron content (TEC). I plan to utilize the Radar, other scintillation based experiments and imaging systems for coordinated studies in context with aforementioned two objectives. I have plan to initiate such studies here at NARL and therefore I wish to propose the use of Equatorial Atmospheric Radar, along with the instrument available in the surrounding of EAR, like, nighttime imagers and GPS receivers for simultaneous observations from NARL as well as EAR site. I wish to raise complete proposals for such coordinated studies during (i) Space Weather events in the forthcoming high solar activity phase (ii) ESF events in equinoctial periods. The proposal may also include the MU radar ISR capability, if the time slots allow for it, to study the mid-latitude F region vertical drifts under Space Weather events. There have been a few observations all over the globe in this context and would be highly useful to solve complexities related to ionospheric storms. I also wish to utilize the potential of the achieved data from EAR Radar, MU radar, GEONET GPS Network. I request to provide an access to such data.
pyasoda _at_ narl.gov.in
Interests:
Interests with MU/EAR radar: