The Kain–Fritsch convective parameterization (KF) has undergone several modifications over the past decade, primarily driven by feedback from numerical modelers and operational forecasters. These changes aim to improve the scheme's performance in numerical weather prediction while aligning it more closely with observations and cloud-resolving modeling studies. The modifications include: 1. **Updraft Formulation**: - **Minimum Entrainment Rate**: Imposed to prevent widespread light precipitation in marginally unstable environments. - **Variable Cloud Radius**: Adjusted based on larger-scale forcing to promote convective initiation in favorable conditions and suppress it in weak or negative forcing. - **Minimum Cloud Depth Threshold**: Adjusted to allow for deeper convective clouds, particularly in lake-effect snow scenarios. - **Shallow (Nonprecipitating) Convection**: Activated when criteria for deep convection are met but the cloud depth is shallow, and the cloud-base mass flux is based on turbulent kinetic energy (TKE). 2. **Downdraft Formulation**: - A new algorithm is introduced, where downdrafts are formed from air at 150–200 hPa above cloud base and detrain over a deep layer below cloud base. - Downdraft mass flux is estimated based on relative humidity and stability above cloud base, no longer related to vertical wind shear. 3. **Closure Assumption**: - The scheme still eliminates convective available potential energy (CAPE) but calculates it based on an entraining parcel rather than undiluted ascent. These modifications have been implemented to address issues such as widespread light precipitation, underprediction of maximum rainfall, and the need for more realistic cloud depth and precipitation processes. The paper provides a detailed documentation of these changes and their justifications, aiming to enhance the KF scheme's performance in various atmospheric conditions.The Kain–Fritsch convective parameterization (KF) has undergone several modifications over the past decade, primarily driven by feedback from numerical modelers and operational forecasters. These changes aim to improve the scheme's performance in numerical weather prediction while aligning it more closely with observations and cloud-resolving modeling studies. The modifications include: 1. **Updraft Formulation**: - **Minimum Entrainment Rate**: Imposed to prevent widespread light precipitation in marginally unstable environments. - **Variable Cloud Radius**: Adjusted based on larger-scale forcing to promote convective initiation in favorable conditions and suppress it in weak or negative forcing. - **Minimum Cloud Depth Threshold**: Adjusted to allow for deeper convective clouds, particularly in lake-effect snow scenarios. - **Shallow (Nonprecipitating) Convection**: Activated when criteria for deep convection are met but the cloud depth is shallow, and the cloud-base mass flux is based on turbulent kinetic energy (TKE). 2. **Downdraft Formulation**: - A new algorithm is introduced, where downdrafts are formed from air at 150–200 hPa above cloud base and detrain over a deep layer below cloud base. - Downdraft mass flux is estimated based on relative humidity and stability above cloud base, no longer related to vertical wind shear. 3. **Closure Assumption**: - The scheme still eliminates convective available potential energy (CAPE) but calculates it based on an entraining parcel rather than undiluted ascent. These modifications have been implemented to address issues such as widespread light precipitation, underprediction of maximum rainfall, and the need for more realistic cloud depth and precipitation processes. The paper provides a detailed documentation of these changes and their justifications, aiming to enhance the KF scheme's performance in various atmospheric conditions.