Four‐dimensional (4D) wind fields were derived from radiance measurements of the Geosynchronous Interferometric Infrared Sounder (GIIRS) onboard the FengYun‐4A satellite with 15‐min temporal ...resolution during Typhoon Maria (2018). Results are evaluated with independent ERA5 reanalysis, Global Data Assimilation System (GDAS) analysis and dropsonde wind profiles, and show a statistical root mean squared error less than 2 m/s for U and V components in troposphere against ERA5 and GDAS. The temporal variation of the wind fields from GIIRS at 15‐min intervals is consistent with that of the hourly ERA5. The added value of wind profiles over the numerical weather predictions (NWP) background field is also revealed. Further experiments confirm that higher temporal resolution from geostationary infrared (IR) sounder measurements could provide better dynamic information. 4D dynamic information can be extracted from high temporal resolution geostationary hyperspectral IR radiances in a consistent and continuous manner that can be used together with the thermodynamic information for various quantitative applications such as NWP data assimilation, near real‐time weather monitoring, situational awareness and nowcasting.
Plain Language Summary
A geostationary hyperspectral infrared (IR) sounder not only provides continuous observations of atmospheric thermodynamic information, but also provides continuous dynamic information critical for weather monitoring, warning, and forecast. The atmospheric motion vectors (AMVs) based on the geostationary imager observations using tracking techniques have been widely used in weather analysis and forecast. However, the retrieval of three‐dimensional atmospheric wind fields from geostationary hyperspectral sounder measurements have not been well studied although a strong argument in favor of the realization of such an instrument has been the derivation of wind fields from moisture structures. The main reason is the lack of real observations from space. Using 15‐min Geosynchronous Interferometric Infrared Sounder observations, an algorithm has been developed for deriving atmospheric four‐dimensional (4D) wind fields, besides, the impacts of temporal resolution, cloudiness, and temporal information on 4D wind fields, respectively, are also studied. It indicates that both temporal and spatial information contributes to the 4D wind fields, and higher temporal resolution provides better 4D wind fields than the lower temporal resolution.
Key Points
Hyperspectral infrared radiances with high temporal resolution from geostationary (GEO) satellite provide four‐dimensional (4D) wind fields
The 4D wind fields can be extracted quantitatively with root mean squared error less than 2 m/s for U and V components of wind in troposphere against ERA5
Higher temporal resolution from GEO measurements provides better wind profile information than lower temporal resolution
Satellite precipitation product estimates (SPPEs) provide rainfall data on regional and global scales and have the potential to be applied in various fields. Several satellite precipitation estimates ...are available for their various features in retrieval algorithms, used sensor instrument, spatial–temporal resolution, and coverage area. Global Satellite Mapping of Precipitation (GSMaP), Integrated MultisatellitE Retrievals (IMERG), and Climate Hazards Group Infrared Precipitation with Station (CHIRPS) are global coverage precipitation datasets with high spatial resolution (0.1°–0.05°) and high temporal resolution (from 30 min to daily updates). The objective of this study was to assess the performance of GSMaP, IMERG, and CHIRPS over Bali Island from 2015 to 2017 in terms of ground rain gauge data over a high density of rain gauge stations (27 in-situ rain gauges) and at various elevations, rainfall intensities, and temporal scales (i.e., daily, penta-days, monthly, and seasonal). A traditional point-to-pixel-based method along with a new introduced continuous, categorical, and volumetric statistical indices comparison approach were implemented to evaluate satellite products. The assessment results demonstrated that IMERG products achieved the highest performance on daily, penta-day, and seasonal time scales, whereas CHIRPS outperformed the other two products on the monthly time scale. Moreover, IMERG was more efficient in detecting rainfall events at different altitudes, but it tended to overestimate rainfall events at high altitudes. With respect to their abilities to detect rainfall events, GSMaP, IMERG, and CHIRPS tended to underestimate the frequency of light rainfall events (0–1 mm/day) and heavy rainfall events (>50 mm/day) but overestimate the frequency of moderate rainfall events (5–10 mm/day). Our result not only highlight IMERG products exhibited better performance in comparison to GSMaP and CHIRPS in Bali Island but also recommend that further improvement on the precipitation estimate algorithm is required by considering complex terrain over small island in the maritime continent area.
•Satellite precipitation product estimates (SPPEs) are assessed with dense rain gauges over Bali Island for the first time.•Categorical and volumetric indexes are proposed as the more objectively represents the SPPEs performance.•Performance of SPPEs are analyzed on various temporal scales, topography and rainfall intensity.
Tropical cyclone (TCs) prediction has improved in the last decade, but studying their structure and dynamics remains a challenging task due to limited in situ observations. The global navigation ...satellite system (GNSS) technique enables retrieving the state of the troposphere with high accuracy in all weather conditions. In this article, we use GNSS slant total delays (STDs) to verify the quality of the weather models during the passage of the TC Meranti, which was the strongest TC in 2016. STDs observed from 28 GNSS stations in Taiwan are compared with the STDs reconstructed from three meteorological data sets: the weather research and forecasting (WRF) model, the global forecast system (GFS), and the ERA-Interim (ERA) using a 2-D ray-tracing technique. Furthermore, two strategies were tested-including and excluding the delays due to liquid and ice water content. The results reveal a good consistency between the GNSS and the ray-traced STDs. The best agreement was found for the WRF, with a mean difference of −0.5 mm and a standard deviation of 29.4 mm when the hydrometeor delay was included. The mean hydrometeor contribution reached up to 2.8 mm for the WRF, while for the ERA and GFS, the contribution to the total delay was negligible. The recorded absolute percent differences were greater for the northern HENC station (mostly within 0.8%) than for the southern GOLI station (on average below 0.5%) due to a closer location to the passing Meranti. The most significant biases were seen in the ERA (around 7%) and the GFS (exceeding −3%) for the PLIM station, located in the central mountain range valley.
Knowledge of cloud properties like cloud top height (CTH) is essential to understand their impact on the earth's radiation budget and on climate change. High spectral resolution measurements from the ...Atmospheric Infrared Sounder (AIRS) are well suited to reveal valuable information about cloud altitude. The CTH retrievals derived from AIRS single field‐of‐view (FOV) radiance measurements are compared with the operational MODIS (Moderate Resolution Imaging Spectroradiometer) cloud product, and Level 2 products obtained from radar and lidar instruments onboard the EOS (Earth Observing System) CloudSat and the CALIPSO (Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation) satellites. Two cases containing a variety of cloud conditions have been studied, and the strengths/shortcomings of CTH products from infrared (IR) sounder radiances are discussed.
In March 2019, Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG)-Final v6 (hereafter IMERG6) was released, with data concerning precipitation dating back to June ...2000. The National Aeronautics and Space Administration (NASA) has suggested that researchers use IMERG6 to replace the frequently used Tropical Rainfall Measuring Mission (TRMM)-3B42 v7 (hereafter TRMM7), which is expected to cease operation in December 2019. This study aims to evaluate the performance of IMERG6 and TRMM7 in depicting the variations of summer (June, July, and August) precipitation over Taiwan during the period 2000–2017. Data used for the comparison also includes IMERG-Final v5 (hereafter IMERG5) and Global Satellite Mapping of Precipitation for Global Precipitation Measurement (GSMaP)-Gauge v7 (hereafter GSMaP7) during the summers of 2014–2017. Capabilities to apply the four satellite precipitation products (SPPs) in studying summer connective afternoon rainfall (CAR) events, which are the most frequently observed weather patterns in Taiwan, are also examined. Our analyses show that when using more than 400 local rain-gauge observations as a reference base for comparison, IMERG6 outperforms TRMM7 quantitatively and qualitatively, more accurately depicting the variations of the summer precipitation over Taiwan at multiple timescales (including mean status, daily, interannual, and diurnal). IMERG6 also performs better than TRMM7 in capturing the characteristics of CAR activities in Taiwan. These findings highlight that using IMERG6 to replace TRMM7 adds value in studying the spatial-temporal variations of summer precipitation over Taiwan. Furthermore, the analyses also indicated that IMERG6 outperforms IMERG5 and GSMaP7 in the examination of most of the features of summer precipitation over Taiwan during 2014–2017.
Intense economic and industrial development in China has been accompanied by severe local air pollution, as well as in other downwind countries in East Asia. This study analyzes satellite ...observational data of sulfur dioxide (SO2), nitrogen dioxide (NO2), and aerosol optical depth (AOD) to explore the spatial distribution, long-term temporal variation, and correlation to meteorological conditions over this region over the period 2005–2015. SO2 and NO2 data are retrieved from the ozone monitoring instrument (OMI) onboard the National Aeronautics and Space Administration (NASA) Aura satellite, while AOD data are from the moderate-resolution imaging spectroradiometer (MODIS) onboard the NASA Aqua satellite. Spatial distributions of SO2, NO2, and AOD show the highest levels in the North China Plain (NCP), with hotspots also in Southeastern China (SC) and the Sichuan Basin (SB). Biomass burning also contributes to a high level of AOD in Southeast Asia in spring and in Equatorial Asia in fall. Considering the correlation of pollutant levels to meteorological conditions, monitoring data show that higher temperature and higher relative humidity (RH) favor the conversion of SO2 and NO2 to sulfate and nitrate aerosol, respectively. The impact of stronger lower tropospheric stability facilitates the accumulation of SO2 and NO2 in NCP and SC. Transport of SO2 and NO2 from intense source regions to relatively clean regions is highly influential over East Asia; such transport from the NCP leads to a considerable increase of pollutants in SC, SB, Taiwan Island (TW), and Taiwan Strait (TWS), particularly in winter. Aerosols generated by biomass burning in Southeast Asia and anthropogenic aerosol in SC are transported to TW and TWS and lead to the increase of AOD, with the highest levels of AOD in SC, TW, and TWS occurring in spring. Precipitation results in the removal of pollutants, especially in highly polluted regions, the effect of which is most significant in winter and spring.
The information on cloud properties and microphysical characteristics is critical for environmental research and application, such as that on weather, climate, hydrology, and green energy and Earth ...energy budget. The launch of the new‐generation geostationary satellite, for example, the Japanese Himawari‐8, enables retrieval of cloud information through multichannel observation. To confirm the retrievals from the Advanced Himawari Imager (AHI) onboard Himawari‐8 (Himawari‐8/AHI), this study accessed the cloud retrievals from AHI and compare them against those obtained from spaceborne passive and active sensors on the low Earth orbit satellites, such as NASA's CloudSat, Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). The atmospheric thermodynamic state from in situ radiosonde provides another dimension for evaluating the retrieved cloud‐top temperature and height, which were obtained and analyzed during two research cruises over the South China Sea during monsoon onset season with large cloud variability to ensure the comprehensive intercomparisons. The findings show that the cloud‐top altitude, cloud optical thickness, and cloud effective particle radius retrieved from AHI are consistent with passive Moderate Resolution Imaging Spectroradiometer (MODIS) data. Furthermore, both spaceborne active Cloud Priofiling Radar (CPR) and Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP) data confirm the low uncertainty of cloud‐top altitude, particularly when the cloud is optically thick. Large cloud‐top altitude discrepancy among these data in the optically thin cloud might be due to the limited AHI spectral channels or instrumental spatial resolutions. The cloud‐top temperature and altitudes in either liquid or ice phase cloud agree well with collocated sounding profiles, with low difference of 1 K and 170 m, respectively.
Key Points
Cloud microphysical properties were retrieved from a geostationary satellite
These properties were accessed by geostationary and polar orbits satellites and in situ radiosonde observations in complex cloud region
Retrieved cloud information from Himawari‐8/AHI agreed with passive and active sensor and in situ radiosonde data
The change of surface vegetation also links to the evapotranspiration pattern so that the moisture flux might be affected by the atmospheric stratiform or convective clouds, meant to be important in ...balancing hydrological cycle and the more analysing is necessary to explain this phenomenon. The aim of this paper to analyze the complex phenomenon that link in spatial correlation of cloud response towards land surface change that ensued from cloud microphysical components. Fourteen years from 2003 to 2016 over Indonesia was applied that issued by Moderate-Resolution Imaging Spectroradiometer (MODIS) level-3 (L3) provides both cloud and land surface products. Cloud microphysical features consist of cloud fraction, cloud top pressure, cloud optical thickness, and cloud effective radius, whereas Normalized Difference Vegetation Index (NDVI) was applied to identify the land surface change. The distribution of spatial correlation and probability distribution function are used as the method to determine each cloud microphysical components response to land surface change. Concerning annual result, desirable connections among correlation between NDVI and cloud parameters is rather widely. Probabilistic approach from statistical analysis in the wet season forms palpably pattern (parabolic pattern) rather than a dry season pattern. Correlation values based on spatial analysis between NDVI anomalies and cloud parameter anomalies have a range of values around -0.8 to 0.8. Throughout Indonesia, every correlation between NDVI anomalies and cloud parameter anomalies has a negative correlation. Sumatra, Kalimantan and Papua have a major role to inject negative correlations. This causes this area to be covered with oil palm plantations.
This study investigates the Global Navigation Satellite System (GNSS) radio occultation (RO) data from FORMOSAT-7/COSMIC-2 (FS7/C2), which provides considerably more and deeper profiles at lower ...latitudes than those from the former FORMOSAT-3/COSMIC (FS3/C). The statistical analysis of six-month RO data shows that the rate of penetration depth below 1 km height within ±45° latitudes can reach 80% for FS7/C2, significantly higher than 40% for FS3/C. For verification, FS7/C2 RO data are compared with the observations from chartered missions that provided aircraft dropsondes and on-board radiosondes, with closer observation times and distances from the oceanic RO occultation over the South China Sea and near a typhoon circulation region. The collocated comparisons indicate that FS7/C2 RO data are reliable, with small deviations from the ground-truth observations. The RO profiles are compared with collocated radiosondes, RO data from other missions, global analyses of ERA5 and National Centers for Environmental Prediction (NCEP) final (FNL), and satellite retrievals of NOAA Unique Combined Atmospheric Processing System (NCAPS). The comparisons exhibit consistent vertical variations, showing absolute mean differences and standard deviations of temperature profiles less than 0.5 °C and 1.5 °C, respectively, and deviations of water vapor pressure within 2 hPa in the lower troposphere. From the latitudinal distributions of mean difference and standard deviation (STD), the intertropical convergence zone (ITCZ) is evidentially shown in the comparisons, especially for the NUCAPS, which shows a larger deviation in moisture when compared to FS7/C2 RO data. The sensitivity of data collocation in time departure and spatial distance among different datasets are presented in this study as well.
To compensate for the emissions missed or underestimated in the national bottom-up emission inventories, we apply the high spatial resolution satellite data from TROPOspheric Monitoring Instrument ...(TROPOMI) to estimate the top-down nitrogen oxide (NOx) emissions in regional scales. The NOx chemical lifetime is derived based on ground-based measurements of ozone photolysis rate, ultra-violet (UV) index, and temperature. For five designated regions of western Taiwan, the derived lifetime is about 1–2 h in summer and 2–4 h in winter. The retrieved 2021 annual emissions for regions near two major pollution sources, Taichung thermal power plant and Mailiao Industrial Zone, are comparable with the emission from the Continuous Emission Monitoring System (CEMS), with a difference of 6% and −12%, respectively. After validating the data and methods, the NOx emissions for five regions of western Taiwan are derived and applied to evaluate the bottom-up inventories. For northern and southern Taiwan, the top-down emissions agree well with emission inventories. The top-down emissions are 12%, 23%, and 16% higher than emission inventories for north-central, central, and south-central Taiwan, respectively. This indicates that the bottom-up inventories are underestimated from north-central to south-central Taiwan, which may be associated with the uncertainties from traffic sources. Given the various complex pollution sources, deriving NOx emissions from space allows us to acquire a better understanding of emissions on urban scales and improve the bottom-up emission inventories.
•The NOx chemical lifetime is derived using ground-based measurements.•The top-down emissions of major pollution sources are comparable with emissions from the monitoring system.•The bottom-up inventories are underestimated in certain cities.•The data with derived lifetime and methods allow us to monitor the NOx emissions in megacities.
PDF
