https://www.bing.com/images/search?view=detailv2&ccid=4gaj08ec&id=15b827d717e11e 07790F5BCC0A4E13BBD103123C&thid=OIP.4gaj08EcIqXuIdGNdiwwUAEsDI&q=monsoon+pi ctures&simid=608027853209010910&selectedindex=119&mode=overlay&first=1 Interference of the Equatorial Waves on the 2017 Indian Monsoon Northward Progression Sue Chen, Maria Flatau, Jerome Schmidt, Craig Bishop Naval Research Laboratory Monterey, CA Sixth WMO International Workshop on Monsoons, 13-17 November 2017, Singapore
Outlines Background for the bogus ISM onset Large-scale conditions of the 2017 Indian Summer Monsoon (ISM) onset Modeling approach: full-physics Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) idealized equatorial wave framework Results from the idealized COAMPS equatorial wave experiments
Flatau et al. (J. of Climate, 2001, JGR 2003) The bogus ISM onset can be triggered by a sequence of events 1. Warm Bay of Bengal (BoB) SST in late spring, Cooling of in May from ISO, TC, or monsoon depression 2. Equatorial westerly vertical shear 3. Presence of MJO, Kelvin, or Rossby waves at the equator
1. Through what mechanisms do the Equatorial Waves interfere with the ISM onset? Scientific Questions 2. What is the role of the reversal of SST in the Bay of Bengal for the bogus ISM onset? https://www.bing.com/images/search?view=detailv2&ccid=%2f% 2BFZplaF&id=978CEB450E0FA8C3106805DB16F90B3012CD5F20&t hid=oip._-fzplafqfvjflh1bgw1aesdh&q=monsoon+pictures&simid=608017485139543 846&selectedindex=137&mode=overlay&first=1
India Meteorological Department (IMD) http://www.imd.gov.in/pages/monsoon_main.php June 1 June 6
Rainfall of 2017 ISM NOAA CPC rain analysis May 25 June 6 June 1 Multiple rain maxima followed by a one week dry period May 25 June 1
MJO & Equatorial wave activity during the 2017 Indian Summer Monsoon TC Mora NOAA CPC OLR analysis
US Navy Global Environmental Model (NAVGEM) Analysis: May 29 TC Mora CC Kelvin Wave
US Navy Global Environmental Model (NAVGEM) Analysis: June 1 CC Rossby Wave
US Navy Global Environmental Model (NAVGEM) Analysis: June 12 ISM
NAVGEM Zonal and Meridional Vertical Wind Shear (200-850 hpa) 5S-5N, 90-100E Meridional Hadley Circulation index
Air-Ocean-Wave-ICE-LSM-Hydro Coupled COAMPS Forecast and Data Assimilation System Atmos OBS obs, remote sensing, text GLOBE WVS Climo User configurable 6 or 12 hr atmosphere update cycle ESMF/NUOPC NAVGEM ATMOSPHERE BC (ANALYSIS) NAVDAS COAMPS GALWEN-LIS Atmosphere Setup LSM Hydrology connector NCODAQC CICE SST, SSH ICE, PROF SHIP, GLDR NCODA NCOM/ROMS SWAN/ WW3 Ocean OBS NCODA QC DATABASE GDEM MODAS DBDBV DBDB2 OSUTide Rivers Ocean Setup WAVE Setup GOFS gww3
Idealized COAMPS Kelvin Wave Experiments May 1 SST Initial 10 m Wind May 28 SST - May 1 SST Bay of Bengal (BoB) Analytical Kelvin wave initialization (Schmidt et al. 2018) E-W periodic boundary conditions 45 km horizontal resolution Aqua planet Full nonlinear physics 1. Dry (no convective feedback), no vertical shear, no radiation 2. Time-invariant (fixed) SST a) Uniform (~30 C) b) Real pre-monsoon NCODA May 1 SST (warm BoB) c) Real May 28 SST from NCODA (cold BoB)
Idealized COAMPS 10 day idealized dry Kelvin wave simulation No vertical shear No surface flux No radiation Chimeric Kelvin Wave Experiments U Wind Chimeric Equatorial waves (Chao, J. of Met. Soci. Japan, 2007) 10 days simulation
Coriolis induces a Rossby wave response behind the idealized, no vertical wind shear, dry-kelvin wave dynamic effect The role of surface enthalpy flux is to advect enthalpy flux toward equator and strengthen the Kelvin wave structure at the equator and suppress the Coriolis induced Rossby wave growth Cold late May SST condition in the BoB favors the growth of the Rossby wave component of Chimeric Kelvin wave Idealized COAMPS Kelvin Wave Experiments U wind, 10 Days simulation, no surface flux Poleward SW flow U wind, 10 Days simulation with surface flux, uniform 32 C SST
U wind, May 1 SST, 4-day simulation Real SST Experiments Unstable dry Rossby Wave emerged after 4 days and last less than 1 day Increased N-S SST gradient in late May 2017 enhanced a small (< 0.2 m/s) SW flow from 0-10N V wind difference May 28 SST-May 1 SST 4-day simulation 10 days idealized dry Kelvin wave simulation No vertical shear With surface flux May 1 and May 28, 2017 real SST No radiation
Dry-Kelvin experiment with May 1 N-S SST gradient Enhanced the poleward meridional flow in the Rossby Wave component of the Chimeric Kelvin wave The poleward meridional flow only reaches ~ 12 N
Rain and 200hPa-800hPa shear difference
Summary The large-scale conditions for the 2017 ISM onset is similar to the bogus ISM onsets discussed by Flatau et al. (2001, 2003) The role of SST (cooling in the BoB) on the Chimeric dry Kelvin wave growth and its influence on induced poleward flow is systematically investigated using four COAMPS idealized experiments in the no vertical shear condition The no surface flux experiment show the Chimeric dry Kelvin wave structure (Kelvin & Rossby) emerged due to the beta effect The real SST idealized experiments showed for Chimeric dry Kelvin wave, the increased SW flow in Rossby wave is not due to colder BoB SST but from increased 0-20N SST gradient in late May A similar result from the moist Chimeric Kelvin wave but is stronger than the dry Chimeric Kelvin wave