Editorial Type:
Article
Article Type:
Research Article

On the Detection of Onset and Activity of the Indian Summer Monsoon Using GPS RO Refractivity Profiles

V. V. M. Jagannadha Rao Department of Physics, Government Polytechnic, Kataram, India

Search for other papers by V. V. M. Jagannadha Rao in
Current site
Google Scholar
PubMed Close
,
M. Venkat Ratnam National Atmospheric Research Laboratory, Gadanki, India

Search for other papers by M. Venkat Ratnam in
Current site
Google Scholar
PubMed Close
,
Y. Durga Santhi Department of Physics, Sri Venkateswara University, Tirupati, India

Search for other papers by Y. Durga Santhi in
Current site
Google Scholar
PubMed Close
,
M. Roja Raman Department of Physics, Sri Venkateswara University, Tirupati, India

Search for other papers by M. Roja Raman in
Current site
Google Scholar
PubMed Close
,
M. Rajeevan National Atmospheric Research Laboratory, Gadanki, India

Search for other papers by M. Rajeevan in
Current site
Google Scholar
PubMed Close
, and
S. Vijaya Bhaskara Rao Department of Physics, Sri Venkateswara University, Tirupati, India

Search for other papers by S. Vijaya Bhaskara Rao in
Current site
Google Scholar
PubMed Close
Print Publication:
01 Jun 2013
DOI:
https://doi.org/10.1175/MWR-D-12-00180.1
Page(s):
2096–2106
Restricted access

Abstract

Global positioning system (GPS) radio occultation (RO) data available during 2001–10 have been used to examine the variations in the refractivity during the onset of Indian summer monsoon (ISM) over the east Arabian Sea (5°–15°N, 65°–75°E). An enhancement of 5–10 N-units in the refractivity is observed around 4.8 km (~600 hPa) a few days (9.23 ± 3.6 days) before onset of the monsoon over Kerala, India. This is attributed to moisture buildup over the Arabian Sea during the monsoon onset phase. A sudden increase (1.5–2 K) in mean upper-tropospheric temperature at the time of onset and during the active phase of the monsoon is attributed to convective activity and the release of latent heat. On the day of monsoon onset over Kerala, an appreciable dip in the refractivity is observed that persisted for 1–3 days followed by an enhancement in refractivity with the active phase of the monsoon. An arbitrary value of 128 N-units difference between 4.8 km (~600 hPa) and 16 km (~100 hPa) coupled with a dip in refractivity on the day of monsoon arrival might give an indication of clear transition of atmospheric conditions and the detection of monsoon onset. Further, a good relation is also found between the activity of monsoon and variability in the refractivity.

Corresponding author address: M. Venkat Ratnam, National Atmospheric Research Laboratory, Department of Space, P.B. No. 123, Gadanki, Tirupati, 517502 India. E-mail: vratnam@narl.gov.in

Abstract

Global positioning system (GPS) radio occultation (RO) data available during 2001–10 have been used to examine the variations in the refractivity during the onset of Indian summer monsoon (ISM) over the east Arabian Sea (5°–15°N, 65°–75°E). An enhancement of 5–10 N-units in the refractivity is observed around 4.8 km (~600 hPa) a few days (9.23 ± 3.6 days) before onset of the monsoon over Kerala, India. This is attributed to moisture buildup over the Arabian Sea during the monsoon onset phase. A sudden increase (1.5–2 K) in mean upper-tropospheric temperature at the time of onset and during the active phase of the monsoon is attributed to convective activity and the release of latent heat. On the day of monsoon onset over Kerala, an appreciable dip in the refractivity is observed that persisted for 1–3 days followed by an enhancement in refractivity with the active phase of the monsoon. An arbitrary value of 128 N-units difference between 4.8 km (~600 hPa) and 16 km (~100 hPa) coupled with a dip in refractivity on the day of monsoon arrival might give an indication of clear transition of atmospheric conditions and the detection of monsoon onset. Further, a good relation is also found between the activity of monsoon and variability in the refractivity.

Corresponding author address: M. Venkat Ratnam, National Atmospheric Research Laboratory, Department of Space, P.B. No. 123, Gadanki, Tirupati, 517502 India. E-mail: vratnam@narl.gov.in
Save
Cover Monthly Weather Review
Monthly Weather Review

  • Ananthakrishnan, R., and M. K. Soman, 1988: The onset of the southwest monsoon over Kerala: 1901–1980. J. Climatol., 8, 283–296.

  • Basha, G., and M. V. Ratnam, 2009: Identification of atmospheric boundary layer height over a tropical station using high-resolution radiosonde refractivity profiles: Comparison with GPS radio occultation measurements. J. Geophys. Res., 114, D16101, doi:10.1029/2008JD011692.

    • Search Google Scholar
    • Export Citation

  • Cook, B. I., and B. M. Buckley, 2009: Objective determination of monsoon season onset, withdrawal, and length. J. Geophys. Res., 114, D23109, doi:10.1029/2009JD012795.

    • Search Google Scholar
    • Export Citation

  • Fasullo, J., and P. J. Webster, 2003: A hydrological definition of Indian monsoon onset and withdrawal. J. Climate, 16, 3200–3211.

  • Flatau, M. K., P. J. Flatau, J. Schmidt, and G. N. Kiladis, 2003: Delayed onset of the 2002 Indian monsoon. Geophys. Res. Lett., 30, 1768, doi:10.1029/2003GL017434.

    • Search Google Scholar
    • Export Citation

  • Gorbunov, M. E., and A. S. Gurvich, 1998: Microlab-1 experiment: Multipath effects in the lower troposphere. J. Geophys. Res., 103 (D12), 13 819–13 826.

    • Search Google Scholar
    • Export Citation

  • Hajj, G. A., E. R. Kursinski, L. J. Romans, W. I. Bertiger, and S. S. Leroy, 2002: A technical description of atmospheric sounding by GPS occultation. J. Atmos. Sol. Terr. Phys., 64, 451–469.

    • Search Google Scholar
    • Export Citation

  • Healy, S. B., 2001: Smoothing radio occultation bending angles above 40 km. Ann. Geophys., 19, 459–468.

  • Huang, C.-Y., and Coauthors, 2010: Impact of GPS radio occultation data assimilation on regional weather predictions. GPS Solutions, 14, 35–49, doi:10.1007/s10291-009-0144-1.

    • Search Google Scholar
    • Export Citation

  • Jagannadha Rao, V. V. M., M. Roja Raman, M. Venkat Ratnam, D. Narayana Rao, and S. V. Bhaskara Rao, 2007: Onset of Indian summer monsoon over Gadanki (13.5°N, 79.2°E): Study using lower atmospheric wind profiler. Geophys. Res. Lett., 34, L22803, doi:10.1029/2007GL031592.

    • Search Google Scholar
    • Export Citation

  • Joseph, P. V., K. P. Sooraj, and C. K. Rajan, 2006: The Summer Monsoon onset process over South Asia and an objective method for the date of monsoon onset over Kerala. Int. J. Climatol., 26, 1871–1893.

    • Search Google Scholar
    • Export Citation

  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77, 437–472.

  • Kursinski, E. R., G. A. Hajj, J. T. Schofield, R. P. Linfield, and K. R. Hardy, 1997: Observing Earth’s atmosphere with radio occultation measurements using the Global Positioning System. J. Geophys. Res., 102 (D19), 23 429–23 465.

    • Search Google Scholar
    • Export Citation

  • Narayana Rao, D., and Coauthors, 2009: Validation of the COSMIC radio occultation data over Gadanki (13.48°N, 79.2°E): A tropical region. Terr. Atmos. Oceanic Sci., 20, 59–70, doi:10.3319/TAO.2008.01.23.01(F3C).

    • Search Google Scholar
    • Export Citation

  • Pai, D. S., and M. N. Rajeevan, 2009: Summer monsoon onset over Kerala: New definition and prediction. J. Earth Syst. Sci., 118, 123–135.

    • Search Google Scholar
    • Export Citation

  • Pearce, R. P., and U. C. Mohanty, 1984: Onset of the Asian summer monsoon 1979–1982. J. Atmos. Sci., 41, 1620–1639.

  • Prasad, V. S., and T. Hayashi, 2005: Onset and withdrawal of Indian summer monsoon. Geophys. Res. Lett., 32, L20715, doi:10.1029/2005GL023269.

    • Search Google Scholar
    • Export Citation

  • Ramesh Kumar, M. R., 2004: Forecasting of onset of southwest monsoon over Kerala coast using satellite data. Geosci. Remote Sens. Lett. IEEE, 1 (4), 265–267, doi:10.1109/LGRS.2004.832226.

    • Search Google Scholar
    • Export Citation

  • Ramesh Kumar, M. R., S. Sankar, and C. Reason, 2009: An investigation into the conditions leading to monsoon onset over Kerala. Theor. Appl. Climatol., 95 (1–2), 69–82, doi:10.1007/s00704-008-0376-y.

    • Search Google Scholar
    • Export Citation

  • Rao, P. L. S., U. C. Mohanty, and K. J. Ramesh, 2005: The evolution and retreat features of the summer monsoon over India. Meteor. Appl., 12, 241–255, doi:10.1017/S1350482705001775.

    • Search Google Scholar
    • Export Citation

  • Rao, U. R., P. S. Desai, P. C. Joshi, and P. C. Pandey, 1998: Early prediction of onset of South west monsoon from ERS-1 Scatterometer winds. Proc. Indian. Acad. Sci. (Earth Planet. Sci.), 107, 33–43.

  • Rocken, C., and Coauthors, 1997: Analysis and validation of GPS/MET data in the neutral atmosphere. J. Geophys. Res., 102 (D25), 29 849–29 866.

    • Search Google Scholar
    • Export Citation

  • Rocken, C., Y. H. Kuo, W. Schreiner, D. Hunt, S. Sokolovskiy, and C. McCormick, 2000: COSMIC system description. Terr. Atmos. Oceanic Sci., 11, 21–52.

    • Search Google Scholar
    • Export Citation

  • Scherllin-Pirscher, B., G. Kirchengast, A. K. Steiner, Y.-H. Kuo, and U. Foelsche, 2011: Quantifying uncertainty in climatological fields from GPS radio occultation: An empirical-analytical error model. Atmos. Meas. Technol., 4, 2019–2034, doi:10.5194/amt-4-2019-2011.

    • Search Google Scholar
    • Export Citation

  • Sharma, R. V., and T. Prasad, 1993: A study of wind index in association with onset of south-west monsoon. Advances in Tropical Meteorology: Meteorology and National Development, R. K. Datta, Ed., Indian Meteorological Society, 217–221.

  • Simon, B., S. H. Rahaman, and P. C. Joshi, 2006: Conditions leading to the onset of the Indiana monsoon: A satellite perspective. Meteor. Atmos. Phys., 93, 201–210, doi:10.1007/s00703-005-0155-6.

    • Search Google Scholar
    • Export Citation

  • Sokolovskiy, S., 2001: Tracking tropospheric radio occultation signals from low Earth orbit. Radio Sci., 36, 483–498, doi:10.1029/1999RS002305.

    • Search Google Scholar
    • Export Citation

  • Sokolovskiy, S., C. Rocken, W. Schreiner, and D. Hunt, 2010: On the uncertainty of radio occultation inversions in the lower troposphere. J. Geophys. Res., 115, D22111, doi:10.1029/2010JD014058.

    • Search Google Scholar
    • Export Citation

  • Soman, M. K., and K. K. Kumar, 1993: Space–time evolution of meteorological features associated with the onset of Indian summer monsoon. Mon. Wea. Rev., 121, 1177–1194.

    • Search Google Scholar
    • Export Citation

  • Taniguchi, K., and T. Koike, 2006: Comparison of definitions of Indian summer monsoon onset: Better representation of rapid transitions of atmospheric conditions. Geophys. Res. Lett., 33, L02709, doi:10.1029/2005GL024526.

    • Search Google Scholar
    • Export Citation

  • Ware, R., and Coauthors, 1996: GPS sounding of the atmosphere from low Earth orbit: Preliminary results. Bull. Amer. Meteor. Soc., 77, 19–40.

    • Search Google Scholar
    • Export Citation

  • Wickert, J., and Coauthors, 2001: Atmosphere sounding by GPS radiooccultation: First results from CHAMP. Geophys. Res. Lett., 28, 3263–3266.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 204 50 1
PDF Downloads 110 22 0