AbstractAbstractA plume model applied to radiosonde observations and the fifth generation ECMWF atmospheric reanalysis (ERA5) is used to assess the relative importance of lower-tropospheric moisture and temperature variability in the convective coupling of equatorial waves. Regression and wavenumber–frequency coherence analyses of satellite precipitation, outgoing longwave radiation (OLR), and plume model estimates of lower-tropospheric vertically integrated buoyancy (〈B〉) are used to identify the spatial and temporal scales where these variables are highly correlated. Precipitation and OLR show little coherence with 〈B〉 when zero entrainment is prescribed in the plume model. In contrast, precipitation and OLR vary coherently with 〈B〉 when “deep inflow” entrainment is prescribed, highlighting that entrainment occurring over a deep layer of the lower troposphere plays an important role in modifying the thermodynamic properties of convective plumes in the tropics. Consistent with previous studies, moisture variability is found to play a more dominant role than temperature variability in the convective coupling of the Madden–Julian oscillation (MJO) and equatorial Rossby (ER) waves, while temperature variability is found to play an important role in the convective coupling of Kelvin (KW) and inertio-gravity (IG) waves. Convective coupling is most strongly impacted by moisture variations in the 925–850- and 825–600-hPa layers for the MJO and ERs, and by 825–600-hPa temperature variations in KWs and IGs, with 1000–950-hPa moist static energy variations playing a relatively small role in convective coupling. Simulations of the Energy Exascale Earth System Model (E3SM), version 2, and a preoperational prototype of NOAA Global Forecast System (GFS) V17 are examined, the former showing unrealistically high coherence between precipitation and 1000-hPa moist static energy, the latter a more realistic relationship.
