Climatology of stratospheric gravity waves and their interaction with zonal mean wind over the tropics using GPS RO and ground-based measurements in the two phases of QBO

The present manuscript deals with the spatial distribution of gravity wave activity over the tropics using ten years (2001–2010) of CHAllenging Mini Payloads (CHAMP) and Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) Global Positioning System (GPS) Radio Occultation (RO) data and ground-based radiosonde measurements over an equatorial station Singapore (1.36°N, 103.98°E) and four tropical stations, Guam (13.48°N, 144.80°E), Palau (7.33°N, 134.48°E) in the northern hemisphere, Darwin (12.41°S, 130.88°E) and Pago-Pago (14.33°S, 170.71°W) in the southern hemisphere from January 2001–December 2010. It also aims to quantify the difference in wave activity in the two phases of QBO, climatologically. Space-time spectra have been constructed over a latitude band of ±10° and decomposing the CHAMP/COSMIC temperature perturbations into symmetric and antisymmetric modes about the equator. Clear signature of equatorial waves with higher wavelength and a constant background of gravity waves (GW) with inertial frequency are prominent in the spectra. Strong GW and mean flow interaction can be seen in the lower stratosphere potential energy density (EP) and momentum flux with enhanced wave activity during the westerly (eastward wind) phase of quasi-biennial oscillation (QBO) (WQBO) over the equatorial and tropical stations like Singapore and Palau/Darwin, respectively. From the latitudinal distribution of energy density, the occurrence of two-peak structure in energy density can be seen in the middle and lower latitudes with an enhancement during the WQBO phase. The EP associated with GWs are calculated at lower stratospheric (19–26 km) heights and are compared with outgoing longwave radiation (OLR) to correlate the wave events with tropical deep convection during the easterly, i.e. westward wind (EQBO) and WQBO phases of QBO. Clear coherence of convection due to Asian summer monsoon with localized enhancement of wave activity over Western Pacific, South America and African region during the WQBO phase is observed at the lower stratospheric heights. Significant enhancement is observed during Northern Hemisphere winter months and minimum during summer. The longitudinally elongated portion of EP over the equator is partially affected by Kelvin wave (KW) like disturbances with short vertical scales and also by inertia GW.

[1]  J. Russell,et al.  Equatorial wave analysis from SABER and ECMWF temperatures , 2007 .

[2]  Emrizal,et al.  Dry Intrusions Following Eastward-Propagating Synoptic-Scale Cloud Systems over Sumatera Island , 2006 .

[3]  J. Holton,et al.  Evidence for short vertical wavelength Kelvin waves in the Department of Energy‐Atmospheric Radiation Measurement Nauru99 radiosonde data , 2001 .

[4]  Matthew C. Wheeler,et al.  Convectively Coupled Equatorial Waves: Analysis of Clouds and Temperature in the Wavenumber–Frequency Domain , 1999 .

[5]  Fan Yi,et al.  High vertical resolution analyses of gravity waves and turbulence at a midlatitude station , 2012 .

[6]  J. Holton,et al.  A Theory of the Quasi-Biennial Oscillation , 1968 .

[7]  T. Maruyama.  Upward Transport of Westerly Momentum due to Disturbances of the Equatorial Lower Stratosphere in th , 1994 .

[8]  Christian Rocken,et al.  A Global Morphology of Gravity Wave Activity in the Stratosphere Revealed by the GPS Occultation Data (GPS/MET) , 2000 .

[9]  S. Sridharan,et al.  Lower stratospheric gravity wave activity over Gadanki (13.5°N, 79.2°E) during the stratospheric sudden warming of 2009: Link with potential vorticity intrusion near Indian sector , 2013 .

[10]  G. North,et al.  Equatorial Waves Including the Madden-Julian Oscillation in TRMM Rainfall and OLR Data , 2004 .

[11]  Paul Berrisford,et al.  Towards a climate data assimilation system: status update of ERA-interim , 2008 .

[12]  T. Tsuda,et al.  Characteristics of 10-day Kelvin Wave Observed with Radiosondes and CHAMP/GPS Occultation during the CPEA Campaign (April-May, 2004) , 2006 .

[13]  J. Wickert,et al.  A global analysis of wave potential energy in the lower stratosphere derived from 5 years of GPS radio occultation data with CHAMP , 2006 .

[14]  F. Yi,et al.  Latitudinal and seasonal variations of inertial gravity wave activity in the lower atmosphere over central China , 2007 .

[15]  Toshitaka Tsuda,et al.  Global distribution of atmospheric waves in the equatorial upper troposphere and lower stratosphere: COSMIC observations of wave mean flow interactions , 2008 .

[16]  Yehui Zhang,et al.  Third‐order resonant interaction of atmospheric gravity waves , 2013 .

[17]  Yoshikazu Hayashi,et al.  Space-Time Spectral Analysis and its Applications to Atmospheric Waves , 1982 .

[18]  J. Holton,et al.  An Updated Theory for the Quasi-Biennial Cycle of the Tropical Stratosphere , 1972 .

[19]  Luo Wei,et al.  The Result of Intensive Radiosonde Observation over Wuhan , 2008 .

[20]  T. Dunkerton,et al.  Estimates of momentum flux associated with equatorial Kelvin and gravity waves , 1997 .

[21]  M. Venkat Ratnam,et al.  Investigation of saturated gravity waves in the tropical lower atmosphere using radiosonde observations , 2010 .

[22]  M. Alexander,et al.  Gravity wave activity during stratospheric sudden warmings in the 2007–2008 Northern Hemisphere winter , 2009 .

[23]  John M. Wallace,et al.  Observational Evidence of Kelvin Waves in the Tropical Stratosphere , 1968 .

[24]  Lucien Froidevaux,et al.  Equatorial Kelvin waves: A UARS MLS view , 1994 .

[25]  T. Dunkerton.  The role of gravity waves in the quasi‐biennial oscillation , 1997 .

[26]  F. Yi,et al.  Latitudinal and seasonal variations of lower atmospheric inertial gravity wave energy revealed by US radiosonde data , 2010 .

[27]  Kaoru Sato,et al.  Short-period disturbances in the equatorial lower stratosphere , 1994 .

[28]  T. Tsuda,et al.  Temporal and spatial distributions of atmospheric wave energy in the equatorial stratosphere revealed by GPS radio occultation temperature data obtained with the CHAMP satellite during 2001–2006 , 2009 .

[29]  T. Tsuda,et al.  Seasonal gravity wave activity observed with the Equatorial Atmosphere Radar and its relation to rainfall information from the Tropical Rainfall Measuring Mission , 2008 .

[30]  Latitudinal and altitudinal variability of lower atmospheric inertial gravity waves revealed by U.S. radiosonde data , 2013 .

[31]  R. Vincent,et al.  Gravity wave activity in the lower atmosphere: Seasonal and latitudinal variations , 1995 .

[32]  J. London,et al.  The quasi‐biennial oscillation in atmospheric ozone , 1982 .

[33]  M. Alexander,et al.  Gravity waves in the tropical lower stratosphere: A model study of seasonal and interannual variability , 2000 .

[34]  M. Alexander,et al.  Interpretations of observed climatological patterns in stratospheric gravity wave variance , 1998 .

[35]  Y. E. Kousky.  On the Relation Between Kelvin Waves and the Quasi-Biennial Oscillation , 1968 .

[36]  S. Rao,et al.  Gravity wave characteristics observed over a tropical station using high-resolution GPS radiosonde soundings , 2009 .

[37]  John M. Wallace,et al.  A Diagnostic Numerical Model of the Quasi-Biennial Oscillation , 1968 .

[38]  T. Tsuda,et al.  Radiosonde observations of equatorial atmosphere dynamics over Indonesia: 2. Characteristics of gravity waves , 1994 .

[39]  F. Yi,et al.  A statistical study of gravity waves from radiosonde observations at Wuhan (30° N, 114° E) China , 2005 .

[40]  J. Gille,et al.  Evidence for Equatorial Kelvin Modes in Nimbus-7 LIMS , 1984 .

[41]  T. Tsuda,et al.  Characteristics of atmospheric gravity wave activity in the polar regions revealed by GPS radio occultation data with CHAMP , 2008 .

[42]  T. Tsuda,et al.  Observations of the diurnal tide during seven intensive radiosonde campaigns in Australia and Indonesia , 2008 .

[43]  M. Yanai,et al.  Stratospheric Wave Disturbances Propagating over the Equatorial Pacific , 1966 .

[44]  J. Russell,et al.  Middle atmospheric thermal structure obtained from Rayleigh lidar and TIMED/SABER observations: A comparative study , 2009 .

[45]  R. Lindzen.  On the development of the theory of the QBO. [Quasi-Biennial Oscillation] , 1987 .

[46]  T. Dunkerton,et al.  Quasi-biennial Modulation of Planetary-Wave Fluxes in the Northern Hemisphere Winter , 1991 .

[47]  Toshitaka Tsuda,et al.  COSMIC GPS Observations of Northern Hemisphere winter stratospheric gravity waves and comparisons with an atmospheric general circulation model , 2008 .

[48]  W. Randel,et al.  Kelvin wave variability near the equatorial tropopause observed in GPS radio occultation measurements , 2005 .

[49]  T. Dunkerton.  Nonlinear Propagation of Zonal Winds in an Atmosphere with Newtonian Cooling and Equatorial Wavedriving , 1991 .

[50]  S. Rao,et al.  Turbulence characteristics over tropical station Gadanki (13.5°N, 79.2°E) estimated using high-resolution GPS radiosonde data , 2010 .

[51]  M. Joan Alexander,et al.  Gravity wave momentum flux in the lower stratosphere over convection , 1995 .

[52]  Murry L. Salby,et al.  Equatorial wave activity derived from fluctuations in observed convection , 1994 .