21. South asian monsoon

21.1. Overview

Three South Asian Summer Monsoon (SASM) namelists for the basic climatology, seasonal cycle, intra-seasonal and inter-annual variability and key teleconnections have been implemented into the ESMValTool focusing on SASM rainfall and horizontal winds in June-September (JJAS). The goal is to provide a comprehensive overview of the basic features of the South Asian Monsoon for a certain model compared to other models, observational and reanalysis data sets for a range of processes and variables relevant to the monsoon.

21.2. Available Namelists and Diagnostics

Namelists are stored in nml/

  • namelist_SAMonsoon_AMIP.xml
  • namelist_SAMonsoon_daily.xml
  • namelist_SAMonsoon.xml

Diagnostics are stored in diag_scripts/

  • SAMonsoon_precip_basic.ncl
  • SAMonsoon_precip_daily.ncl
  • SAMonsoon_precip_domain.ncl
  • SAMonsoon_precip_IAV.ncl
  • SAMonsoon_precip_propagation.ncl
  • SAMonsoon_precip_seasonal.ncl
  • SAMonsoon_teleconnections.ncl
  • SAMonsoon_wind_basic.ncl
  • SAMonsoon_wind_IAV.ncl
  • SAMonsoon_wind_seasonal.ncl

21.3. User settings

User setting files (cfg files) are stored in nml/cfg_SAMonsoon/

  1. SAMonsoon_wind_basic.ncl

    Required diag_script_info attributes

    • styleset: “CMIP5”, “DEFAULT”
    • season: season in letters, e.g., “JJAS”
    • latrange_basic: min. and max. latitude of crop area (array)
    • lonrange_basic: min. and max. longitude of crop area (array)
    • cn_levels_mean_basic: contour levels for mean plots (array)
    • cn_levels_mean_diff_basic: contour levels for mean difference plots (array)
    • cn_levels_stddev_basic: contour levels for standard deviation plots (array)
    • cn_levels_stddev_diff_basic: contour levels for standard deviation difference plots (array)
    • my_region: monsoon region (must be set to “SA”)
  2. SAMonsoon_wind_seasonal.ncl, SAMonsoon_wind_IAV.ncl

    Required diag_sccript_info attributes

    • styleset: “CMIP5”, “DEFAULT”
    • season: season in letters, e.g., “JJAS”
    • multi_model_mean : calculate multi-model mean (“y”, “n”)
  3. SAMonsoon_precip_basic.ncl, SAMonsoon_precip_seasonal.ncl, SAMonsoon_precip.ncl, SAMonsoon_precip_domain.ncl, SAMonsoon_precip_basic_daily.ncl, SAMonsoon_precip_IAV.ncl, SAMonsoon_precip_propagation.ncl

    Required diag_script_info attributes

    • season: season in letters, e.g., “JJAS”

    Settings specific for the precip basic plot_type

    • latrange_basic: min. and max. latitude (2-element array)
    • lonrange_basic: min. and max longitude (2-element array)
    • cn_levels_mean_basic: contour levels for mean plots (n-element array)
    • cn_levels_mean_diff_basic: contour levels for mean difference plots (n-element array)
    • cn_levels_stddev_basic: contour levels for standard deviation plots (n-element array)
    • cn_levels_stddev_diff_basic: contour levels for standard deviation difference plots (n-element array)
    • cn_levels_stddev_norm_basic (only SAMonsoon_precip_basic_daily.ncl): contour levels for standard deviation plots (n-element array)
    • cn_levels_stddev_norm_diff_basic (only SAMonsoon_precip_basic_daily.ncl): contour levels for standard deviation difference plots (n-element array)

    Settings specific for the precip seasonal plot_type (SAMonsoon_precip_seasonal.ncl)

    • latrange_seasonal: min. and max. latitude of crop area (2-element array)
    • lonrange_seasonal: min. and max. longitude of crop area (2-element array)
    • styleset: “CMIP5”, “DEFAULT”
    • multi_model_mean : calculate multi-model mean (“y”, “n”)

    Settings shared by the precip global domain/intensity plot_type

    • summer_season: “MJJAS”
    • winter_season: “NDJFM”

    Settings specific for the precip global domain plot_type

    • latrange_global: min. and max. latitude (2-element array)
    • cn_levels_global_domain_mean: contour levels for global domain plots (array)
    • cn_levels_global_domain_diff: contour levels for global domain difference plots (array)
    • high_intensity_cutoff_mmday: cut-off for monsoon domain definition in mm day-1

    Settings specific for the precip intensity plots

    • cn_levels_intensity_mean: contor levels for intensity mean plots (n-element array)
    • cn_levels_intensity_diff: contor levels for intensity difference plots (n-element array)
    • abs_cmap: path and filename of color map for absolute values
    • diff_cmap: path and filename of color map for difference values
    • my_region: monsoon region (must be set to “SA”)

    Settings specific for daily precipitation plots (SAMonsoon_precip_daily.ncl)

    • isv_latrange: min. and max. latitude of crop area (2-element array)
    • isv_lonrange: min. and max. latitude of crop area (2-element array)
    • bob_latrange: min. and max. latitude of crop area for Bay of Bengal (2-element array)
    • bob_lonrange = min. and max. longitude of crop area for Bay of Bengal (2-element array)
    • eio_latrange: min. and max. latitude of crop area for eastern equatorial Indian Ocean (2-element array)
    • eio_lonrange: min. and max. longitude of crop area for eastern equatorial Indian Ocean (2-element array)
    • filter_min: lower limit used for filtering
    • filter_max: upper limit used for filtering
    • filter_weights: number of filter weights to use

    Settings specific for daily propagation plots (SAMonsoon_precip_propagation.ncl)

    • prop_isv_latrange: min. and max. latitude of crop area (2-element array)
    • prop_isv_lonrange: min. and max. longitude of crop area (2-element array)
    • prop_lag_latrange: min. and max. latitude of crop area for lag computation along longitude (2-element array)
    • prop_lag_lonrange: min. and max. longitude of crop area for lag computation along latitude (2-element array)
    • prop_ref_latrange: min. and max. latitude of crop area for lag reference area (2-element array)
    • prop_ref_lonrange: min. and max. longitude of crop area for lag reference area (2-element array)
    • prop_filter_mxlag: size of lag
    • ihp: Lanczos switch for low/high band pass filter
    • nWgt: total number of weights for Lanczos
    • sigma: Lanczos sigma
    • min_days: min days in filtering
    • max_days: max day in filtering
    • fca: start frequency to compute Lanczos weights
    • fcb: end frequency to compute Lanczos weights
  4. SAMonsoon_teleconnections.ncl

    Required diag_script_info attributes

    • monsoon_latrange: min. and max. latitude of crop area for Indian Monsoon (2-element array)
    • monsoon_lonrange: min. and max. longitude of crop area for Indian Monsoon (2-element array)
    • nino34_latrange: min. and max. latitude of Niño3.4 region (2-element array)
    • nino34_lonrange: min. and max. longitude of Niño3.4 region (2-element array)
    • tele_latrange: min. and max. latitude of crop area for overview area (2-element array)
    • tele_lonrange: min. and max. longitude of crop area for overview area (2-element array)
    • cn_levels_mean_basic: contour levels for mean plot (n-element array)
    • cn_levels_mean_diff_basic: contour levels for mean difference plot (n-element array)
    • cn_levels_stddev_basic: contour levels for standard deviation plot (n-element array)
    • cn_levels_stddev_diff_basic: contour levels for standard deviation difference plot (n-element array)

21.4. Variables

  • pr (atmos, daily/monthly, longitude latitude time)
  • ts (atmos, monthly, longitude latitude time)
  • ua (atmos, monthly, longitude latitude lev time)
  • va (atmos, monthly, longitude latitude lev time)

21.5. Observations and Reformat Scripts

Note: (1) obs4mips data can be used directly without any preprocessing; (2) see headers of reformat scripts for non-obs4mips data for download instructions.

  • ERA-Interim (ua, va, pr – reformat_scripts/obs/reformat_obs_ERA-Interim.ncl, reformat_obs_ERA-Interim_surffluxes.ncl)
  • NCEP (ua, va – reformat_scripts/obs/reformat_obs_NCEP.ncl)
  • TRMM-L3 (pr, monthly means – obs4mips)
  • TRMM_3B42 (pr, daily means – reformat_scripts/obs/reformat_obs_TRMM-3B42-daily.ncl)
  • HadISST (ts – reformat_scripts/obs/reformat_obs_HadISST.ncl)
  • GPCP-1DD (pr, daily means – obs4mips)
  • GPCP-SG (pr, monthly means – obs4mips)
  • MERRA (pr – obs4mips)
  • CMAP (pr – reformat_scripts/obs/reformat_obs_CMAP.ncl)

21.6. References

  • Sperber, K. R., et al., The Asian summer monsoon: an intercomparison of CMIP5 vs. CMIP3 simulations of the late 20th century, Clim Dyn (2013) 41:2711–2744, doi: 10.1007/s00382-012-1607-6, 2012.
  • Lin, Jia-Lin, Klaus M. Weickman, George N. Kiladis, Brian E. Mapes, Siegfried D. Schubert, Max J. Suarez, Julio T. Bacmeister, Myong-In Lee, 2008: Subseasonal Variability Associated with Asian Summer Monsoon Simulated by 14 IPCC AR4 Coupled GCMs. J. Climate, 21, 4541-4567. doi: http://dx.doi.org/10.1175/2008JCLI1816.1.
  • Webster, P. J., and S.Yang, 1992: Monsoon and ENSO: Selectively interactive systems. Quart. J. Roy. Meteor. Soc., 118, 877-926. (Webster-Yang dynamical monsoon index)
  • Goswami, B. N., B. Krishnamurthy, and H. Annamalai, 1999: A broad-scale circulation index for interannual variability of the Indian summer monsoon. Quart. J. Roy. Meteor. Soc., 125, 611-633. (Goswami dynamical monsoon index)
  • Wang, B., and Z. Fan, 1999: Choice of south Asian summer monsoon indices. Bull. Amer. Meteor. Soc., 80, 629-638. (Wang-Fan dynamical monsoon index)
  • Wang B., J. Liu, H. J. Kim, P. J. Webster, and S. Y. Yim, Recent change of global monsoon precipitation (1979-2008), Climate Dynamics, doi: 10.1007/s00382-011-1266-z, 2011. (Intensity/Monsoon domain reference)

21.7. Example plots

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pic_samonsoon_1 pic_samonsoon_2

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