{"id":{"repo_id":"auckland-ms","oai_identifier":"oai:researchspace.auckland.ac.nz:2292/72446"},"canonical_url":"https://search.dev.ndltd.org/etd/auckland-ms/oai:researchspace.auckland.ac.nz:2292/72446","repository":{"repo_id":"auckland-ms","name":"University of Auckland","base_url":"https://researchspace.auckland.ac.nz/server/oai/request"},"display":{"title":"A Study on the Diurnal and Seasonal Cycles of Tropical Cirrus Clouds","abstract":"Tropical cirrus clouds (TCC) regulate the Earth’s radiative energy budget. However, mechanisms of the diurnal and seasonal cycles of their occurrence still require further investigation due to limited observations. This study utilizes observational data from the Cloud-Aerosol Transport System (CATS) and the fifth-generation hourly reanalysis product from the European Centre for Medium-Range Weather Forecasts (ERA5) to investigate the diurnal cycle of TCC occurrence in 2016, between 24◦S and 24◦N. Additionally, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) monthly data, along with ERA5 monthly reanalysis data, are used to investigate the seasonal cycle of TCC occurrence from 2007 to 2015 within the same tropical domain. The ice cloud fraction (ICF) is found to be maximized at a higher altitude of 14 km, compared to the altitudes where ice water contents (IWC) peak—12km and 9km during the diurnal cycle, and 12km during the seasonal cycle. The diurnal cycle of IWC differs from that of ICF; however, the seasonal cycle of IWC is more consistent with that of ICF over time. The diurnal and seasonal cycles of IWC above 10.5km are highly correlated with variations in vertical transport of moisture (VTM). Below 10.5 km, IWC is more associated with the transformation of cloud droplets from liquid to ice. Regarding the ICF on both time scales, relative humidity (RH) plays a dominant role. Increases in water vapor and/or decreases in temperature, along with self-maintenance through cloud radiative processes, are key factors that affect the RH of cloudy regions, thereby regulating the diurnal and seasonal cycles of ICF. A novel method is proposed, categorizing TCC into two types: moist TCC and dry TCC. Moist TCC are associated with convection, as indicated by a positive Δq, which denotes a specific humidity (SPH) that exceeds the time-averaged SPH at the same location. Dry TCC are associated with temperature perturbations resulting from non-convective processes, as indicated by negative ΔT and Δq, with ΔT representing a temperature below the time-averaged temperature at the same location. This method explains how convection and non-convective processes contribute to the TCC occurrence on both time scales.","abstract_html":"Tropical cirrus clouds (TCC) regulate the Earth’s radiative energy budget. However, mechanisms of the diurnal and seasonal cycles of their occurrence still require further investigation due to limited observations. This study utilizes observational data from the Cloud-Aerosol Transport System (CATS) and the fifth-generation hourly reanalysis product from the European Centre for Medium-Range Weather Forecasts (ERA5) to investigate the diurnal cycle of TCC occurrence in 2016, between 24◦S and 24◦N. Additionally, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) monthly data, along with ERA5 monthly reanalysis data, are used to investigate the seasonal cycle of TCC occurrence from 2007 to 2015 within the same tropical domain. The ice cloud fraction (ICF) is found to be maximized at a higher altitude of 14 km, compared to the altitudes where ice water contents (IWC) peak—12km and 9km during the diurnal cycle, and 12km during the seasonal cycle. The diurnal cycle of IWC differs from that of ICF; however, the seasonal cycle of IWC is more consistent with that of ICF over time. The diurnal and seasonal cycles of IWC above 10.5km are highly correlated with variations in vertical transport of moisture (VTM). Below 10.5 km, IWC is more associated with the transformation of cloud droplets from liquid to ice. Regarding the ICF on both time scales, relative humidity (RH) plays a dominant role. Increases in water vapor and/or decreases in temperature, along with self-maintenance through cloud radiative processes, are key factors that affect the RH of cloudy regions, thereby regulating the diurnal and seasonal cycles of ICF. A novel method is proposed, categorizing TCC into two types: moist TCC and dry TCC. Moist TCC are associated with convection, as indicated by a positive Δq, which denotes a specific humidity (SPH) that exceeds the time-averaged SPH at the same location. Dry TCC are associated with temperature perturbations resulting from non-convective processes, as indicated by negative ΔT and Δq, with ΔT representing a temperature below the time-averaged temperature at the same location. This method explains how convection and non-convective processes contribute to the TCC occurrence on both time scales.","abstract_has_math":false,"creators":["Huang, Qin"],"institution":"ResearchSpace@Auckland","degree_name":"PhD","degree_level":"Doctoral","degree_discipline":"Physics","degree_department":null,"school":null,"contributors":[],"advisors":["Dinh, Tra"],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025","date_published":"2025","updated_at":"2026-07-24T01:05:30Z","subjects":["Tropical cirrus clouds","ice water contents","ice cloud fraction","diurnal cycle","seasonal cycle","convection","non-convective processes"],"languages":[],"rights":["Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated."],"rights_urls":["https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm"],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/2292/72446","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Dinh, Tra"]},{"key":"dc:creator","label":"Author","values":["Huang, Qin"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2025-06-10T00:41:02Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2025-06-10T00:41:02Z"]},{"key":"dc:date.issued","label":"Date","values":["2025"]},{"key":"dc:publisher","label":"Institution","values":["ResearchSpace@Auckland"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Physics"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Doctoral"]},{"key":"thesis:degree_name","label":"Degree Name","values":["PhD"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["The University of Auckland"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Tropical cirrus clouds","ice water contents","ice cloud fraction","diurnal cycle","seasonal cycle","convection","non-convective processes"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated."]},{"key":"dc:rights.uri","label":"Rights URI","values":["https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/2292/72446"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Tropical cirrus clouds (TCC) regulate the Earth’s radiative energy budget. However, mechanisms of the diurnal and seasonal cycles of their occurrence still require further investigation due to limited observations. This study utilizes observational data from the Cloud-Aerosol Transport System (CATS) and the fifth-generation hourly reanalysis product from the European Centre for Medium-Range Weather Forecasts (ERA5) to investigate the diurnal cycle of TCC occurrence in 2016, between 24◦S and 24◦N. Additionally, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) monthly data, along with ERA5 monthly reanalysis data, are used to investigate the seasonal cycle of TCC occurrence from 2007 to 2015 within the same tropical domain. The ice cloud fraction (ICF) is found to be maximized at a higher altitude of 14 km, compared to the altitudes where ice water contents (IWC) peak—12km and 9km during the diurnal cycle, and 12km during the seasonal cycle. The diurnal cycle of IWC differs from that of ICF; however, the seasonal cycle of IWC is more consistent with that of ICF over time. The diurnal and seasonal cycles of IWC above 10.5km are highly correlated with variations in vertical transport of moisture (VTM). Below 10.5 km, IWC is more associated with the transformation of cloud droplets from liquid to ice. Regarding the ICF on both time scales, relative humidity (RH) plays a dominant role. Increases in water vapor and/or decreases in temperature, along with self-maintenance through cloud radiative processes, are key factors that affect the RH of cloudy regions, thereby regulating the diurnal and seasonal cycles of ICF. A novel method is proposed, categorizing TCC into two types: moist TCC and dry TCC. Moist TCC are associated with convection, as indicated by a positive Δq, which denotes a specific humidity (SPH) that exceeds the time-averaged SPH at the same location. Dry TCC are associated with temperature perturbations resulting from non-convective processes, as indicated by negative ΔT and Δq, with ΔT representing a temperature below the time-averaged temperature at the same location. This method explains how convection and non-convective processes contribute to the TCC occurrence on both time scales."]},{"key":"dc:title","label":"Title","values":["A Study on the Diurnal and Seasonal Cycles of Tropical Cirrus Clouds"]}]}],"canonical_facts":{"dc:contributor.advisor":["Dinh, Tra"],"dc:creator":["Huang, Qin"],"dc:date.accessioned":["2025-06-10T00:41:02Z"],"dc:date.available":["2025-06-10T00:41:02Z"],"dc:date.issued":["2025"],"dc:description.abstract":["Tropical cirrus clouds (TCC) regulate the Earth’s radiative energy budget. However, mechanisms of the diurnal and seasonal cycles of their occurrence still require further investigation due to limited observations. This study utilizes observational data from the Cloud-Aerosol Transport System (CATS) and the fifth-generation hourly reanalysis product from the European Centre for Medium-Range Weather Forecasts (ERA5) to investigate the diurnal cycle of TCC occurrence in 2016, between 24◦S and 24◦N. Additionally, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) monthly data, along with ERA5 monthly reanalysis data, are used to investigate the seasonal cycle of TCC occurrence from 2007 to 2015 within the same tropical domain. The ice cloud fraction (ICF) is found to be maximized at a higher altitude of 14 km, compared to the altitudes where ice water contents (IWC) peak—12km and 9km during the diurnal cycle, and 12km during the seasonal cycle. The diurnal cycle of IWC differs from that of ICF; however, the seasonal cycle of IWC is more consistent with that of ICF over time. The diurnal and seasonal cycles of IWC above 10.5km are highly correlated with variations in vertical transport of moisture (VTM). Below 10.5 km, IWC is more associated with the transformation of cloud droplets from liquid to ice. Regarding the ICF on both time scales, relative humidity (RH) plays a dominant role. Increases in water vapor and/or decreases in temperature, along with self-maintenance through cloud radiative processes, are key factors that affect the RH of cloudy regions, thereby regulating the diurnal and seasonal cycles of ICF. A novel method is proposed, categorizing TCC into two types: moist TCC and dry TCC. Moist TCC are associated with convection, as indicated by a positive Δq, which denotes a specific humidity (SPH) that exceeds the time-averaged SPH at the same location. Dry TCC are associated with temperature perturbations resulting from non-convective processes, as indicated by negative ΔT and Δq, with ΔT representing a temperature below the time-averaged temperature at the same location. This method explains how convection and non-convective processes contribute to the TCC occurrence on both time scales."],"dc:identifier.uri":["https://hdl.handle.net/2292/72446"],"dc:publisher":["ResearchSpace@Auckland"],"dc:rights":["Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated."],"dc:rights.uri":["https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm"],"dc:subject":["Tropical cirrus clouds","ice water contents","ice cloud fraction","diurnal cycle","seasonal cycle","convection","non-convective processes"],"dc:title":["A Study on the Diurnal and Seasonal Cycles of Tropical Cirrus Clouds"],"dc:type":["Thesis"],"thesis:degree_discipline":["Physics"],"thesis:degree_level":["Doctoral"],"thesis:degree_name":["PhD"],"thesis:institution_name":["The University of Auckland"]},"updated_at":"2026-07-24T01:05:30Z"}