The CLAUS project has developed a global archive of high-resolution (3-hourly, 0.5° latitude–longitude grid) window (11–12 μm) brightness temperature (Tb) data from multiple satellites. This dataset has been used to construct a climatology of the diurnal cycle in convection, cloudiness, and surface temperature for all regions of the Tropics. The study demonstrates that the diurnal cycle characteristics are universal for land versus ocean, clear sky versus convective regimes. Oceanic deep convection peaks in the early morning, while continental convection generally peaks in the evening, with regional variations due to complex land–sea and mountain–valley breezes and mesoscale convective systems. The strong diurnal signal over land spreads over adjacent oceans, likely through gravity waves. The CLAUS data have been used to evaluate the UK Met Office Unified Model (UM), version HadAM3. The model struggles to capture the observed phase of the diurnal cycle in convection, indicating issues in its physical parameterizations. The diurnal cycle analysis is a powerful tool for identifying and correcting model deficiencies. The CLAUS dataset provides a good climatology of tropical brightness temperature and convective activity. It also offers a good measure of tropical variability, particularly the degree to which that variability is associated with intradiurnal timescales. The study shows that the diurnal cycle in brightness temperature and derived precipitation varies significantly across different regions. The amplitude and phase of the diurnal cycle are consistent with previous studies, with land clear sky regions showing a maximum in Tb shortly after noon, while oceanic regions show a maximum in the early morning. The phase of the diurnal cycle in precipitation and Tb is consistent with observations, with a maximum in deep convection in the late afternoon and evening over land and in the early morning over oceans. The CLAUS data also show that the diurnal cycle spreads over oceans, likely through gravity waves. The study highlights the importance of the diurnal cycle in modulating monsoon rainfall and the influence of orography on the phase of the diurnal cycle. The results demonstrate that the diurnal cycle varies significantly across different regions, with the largest amplitudes over clear sky continents and the smallest over oceanic regions. The CLAUS data provide a valuable tool for evaluating climate models and understanding the diurnal cycle in the Tropics.The CLAUS project has developed a global archive of high-resolution (3-hourly, 0.5° latitude–longitude grid) window (11–12 μm) brightness temperature (Tb) data from multiple satellites. This dataset has been used to construct a climatology of the diurnal cycle in convection, cloudiness, and surface temperature for all regions of the Tropics. The study demonstrates that the diurnal cycle characteristics are universal for land versus ocean, clear sky versus convective regimes. Oceanic deep convection peaks in the early morning, while continental convection generally peaks in the evening, with regional variations due to complex land–sea and mountain–valley breezes and mesoscale convective systems. The strong diurnal signal over land spreads over adjacent oceans, likely through gravity waves. The CLAUS data have been used to evaluate the UK Met Office Unified Model (UM), version HadAM3. The model struggles to capture the observed phase of the diurnal cycle in convection, indicating issues in its physical parameterizations. The diurnal cycle analysis is a powerful tool for identifying and correcting model deficiencies. The CLAUS dataset provides a good climatology of tropical brightness temperature and convective activity. It also offers a good measure of tropical variability, particularly the degree to which that variability is associated with intradiurnal timescales. The study shows that the diurnal cycle in brightness temperature and derived precipitation varies significantly across different regions. The amplitude and phase of the diurnal cycle are consistent with previous studies, with land clear sky regions showing a maximum in Tb shortly after noon, while oceanic regions show a maximum in the early morning. The phase of the diurnal cycle in precipitation and Tb is consistent with observations, with a maximum in deep convection in the late afternoon and evening over land and in the early morning over oceans. The CLAUS data also show that the diurnal cycle spreads over oceans, likely through gravity waves. The study highlights the importance of the diurnal cycle in modulating monsoon rainfall and the influence of orography on the phase of the diurnal cycle. The results demonstrate that the diurnal cycle varies significantly across different regions, with the largest amplitudes over clear sky continents and the smallest over oceanic regions. The CLAUS data provide a valuable tool for evaluating climate models and understanding the diurnal cycle in the Tropics.