Atmospheric Water Vapor Research Articles

Satellite-Based Remote Sensing of Atmospheric Water Vapor Over Oceans: An Inter-Comparison Against Shipborne GNSS Observations

Satellite-Based Remote Sensing of Atmospheric Water Vapor Over Oceans: An Inter-Comparison Against Shipborne GNSS Observations

Design and Evaluation of a Desiccant-based Solar Still for Atmospheric Water Collection

A novel still design is proposed that employs a composite desiccant to adsorb atmospheric water vapor. The still has a pyramid design with two short windows and two large glass surfaces. The still is designed to be partially buried 15 centimeters into the ground for passive cooling of the condensing glass surfaces to improve condensation efficiency. An experimental setup is developed with a mud platform to study the performance of the still. A pyramid-shaped still of dimension 30cm x 30cm x 45cm (LxWxH) is fitted with thermocouples, humidity sensors, and a pyranometer to record the global irradiance. The data for two days, one with a buried still and the other unburied, of similar irradiance, are recorded from 6 am to 6 pm with a beaker containing water placed at the stage in the still. The results indicate a drop in glass temperature of about 10.42% in the buried setup compared to the unburied structure. This also resulted in the dew point being maintained for only 35% of the time in the unburied still compared to the buried still.

Tightly Coupled Tomography Model for Atmospheric Water Vapor Based on Multisource Remote-Sensing and GNSS Data

Tightly Coupled Tomography Model for Atmospheric Water Vapor Based on Multisource Remote-Sensing and GNSS Data

Atmospheric water recycling an essential feature of critical natural asset stewardship

Abstract Non-technical summary In this paper, we explore how critically important ecosystems on the land provide evaporation to the atmosphere, which will later fall as precipitation elsewhere. Using a model-based analysis that tracks water flowing through the atmosphere, we find that more than two-thirds of the precipitation over critically important ecosystem areas is supplied by evaporation from other land. Likewise, more than 40% of the evaporation from critically important ecosystems falls as precipitation on other land. We conclude our work by discussing the policy implications for how these critically important ecosystems connect spatially distant wild and working lands via the atmospheric water cycle. Technical summary Global ecosystems are interconnected via atmospheric water vapor flows. Land use change can modify evaporation from land, altering atmospheric moisture recycling and potentially leading to significant changes in downwind precipitation and associated ecological impacts. We combine insights on global ecosystem-regulated moisture recycling with an analysis of critical natural assets (CNA, the 30% of global land providing most of nature's contributions to people) to reveal the sources and sinks of atmospheric water cycle regulation. We find that 65% of the precipitation over CNA is supplied by evaporation from other land areas. Likewise, CNA regions supply critical moisture as precipitation to terrestrial natural ecosystems and production systems worldwide, with 44% of CNA evaporation falling on terrestrial surfaces. Specifically, the Congo River basin emerges as a hotspot of overlap between local atmospheric water cycle maintenance and concentration of nature's contributions to people. Our results suggest global priority areas for conservation efforts beyond and in support of CNA, emphasizing the importance of sparsely populated managed forests and rangelands, along with wild forests, for fostering moisture recycling to and within CNA. This work also underlines the manifold benefits associated with achieving United Nations Sustainable Development Goal #15, to sustainably manage terrestrial life and conserve biodiversity. Social media summary Critically important ecosystems are essential for connecting distant landscapes via the atmospheric water cycle.

Observation of Atmospheric Water Vapor and Its Stable Isotopes at the Seaside Based on Fourier Transform Infrared Spectroscopy

Observation of Atmospheric Water Vapor and Its Stable Isotopes at the Seaside Based on Fourier Transform Infrared Spectroscopy

Recycling Glass Fiber from Polyurethane Composite by Pyrolysis Strategy with High Mechanical Properties

With the rapid advancement of the wind power industry, the recycling of retired wind turbine blades and the regeneration of glass fibers have become urgent environmental and economic issues. In this article, a two-step pyrolysis strategy was put forward, in which the relationship between the pyrolysis parameters and the properties of the recycled glass fibers, including the surface morphology, defects, and mechanical properties were demonstrated. We found that pyrolyzing the composites at 500°C under high-temperature water vapor atmosphere to recover the glass fibers, and oxidizing at 450°C to remove the residual carbon of fibers is the optimal choice. In this way, not only can the fibers be recovered from the waste composites, but also the mechanical properties of the fibers can be retained while removing the residual carbon on the surface, which provides a guarantee for subsequent high-value reuse of waste fan blade composite materials.

Water content of rocky exoplanets in the habitable zone

In this study we investigated the interiors of rocky exoplanets in order to identify those that may have large quantities of water. We modelled the interiors of 28 rocky exoplanets, assuming four different layers – an iron core, a rock mantle, a high-pressure ice layer, and a surface ice/water layer. Due to observational bias, our study is limited to habitable zone exoplanets. We determined a range of possible water mass fractions for each planet consistent with the modelled planetary structures. We calculated the tidal heating experienced by these exoplanets through gravitational interactions with their host stars, assuming a temperature- and composition-dependent Maxwell viscoelastic rheology. Assuming radioactive elemental abundances observed in Solar System meteorites, we also calculated the radiogenic heat flux inside the planets. We estimated the probability of the presence of a thick ocean layer in these planets, taking into account the effect of both tidal and radiogenic heating. Our results showed that Proxima Centauri b, Ross 128 b, Teegarden’s b and c, GJ 1061 c and d, and TRAPPIST-1 e may have an extended liquid water reservoir. Furthermore, extremely high H2O-content of the exoplanets Kepler-62 f, Kepler-1652 b, Kepler-452 b, and Kepler-442 b suggests that these planets may maintain a water vapour atmosphere and may in fact be examples of larger ocean worlds. Upon the discovery of new rocky exoplanets beyond the habitable zone, our study can be extended to icy worlds.

EXPERIMENTAL STUDY OF CONDENSATION OF WATER ON POLYDIMETHYLSILOXANE-COATED COPPER SURFACES

Modification of surfaces to enable dropwise condensation (DWC) is a promising approach for achieving high condensation rates. In this work, we present an experimental study on condensation of water on copper surfaces coated with an ultrathin, 5-10 nm thick polydimethylsiloxane (PDMS) layer. This hydrophobic coating possesses a very low thermal resistance, which in combination with copper substrate enables achieving high condensation rates in heat transfer applications. The PDMS-coated copper substrates have been fabricated with a newly developed method, which involves turning, sanding, polishing, oxidation, and polymer coating steps. The measured static contact angle was 110° ± 1°, and the contact angle hysteresis was 2°. The achieved very low hysteresis is advantageous for promoting DWC. The surface showed no aging effects during 100 repetitions of advancing and receding contact angle (ARCA) measurements. Condensation heat transfer on uncoated and PDMS-coated copper surfaces surfaces has been studied experimentally in a saturated water vapor atmosphere at 60°C. An enhancement factor for heat flux and heat transfer coefficient of up to 1.6 was found on PDMS-coated copper surfaces compared to uncoated surfaces, which decreased to 1.1 on the second and third day of condensation operation. Images of the condensation surface were recorded while conducting condensation experiments and post processed to evaluate drop departure diameter and frequency of drop sweeping events. It has been shown that the behavior of the heat transfer coefficient correlates with the frequency of the sweeping events.

A review of atmospheric water vapor lidar calibration methods

AbstractAtmospheric water vapor is a crucial factor in the Earth's water cycle. As an important greenhouse gas, changes in the spatio‐temporal distribution of atmospheric water vapor can contribute to the occurrence of various extreme weather phenomena. Lidar, with its high spatial and temporal resolutions, has great potential for applications in water vapor profile detection. Raman lidar and differential absorption lidar (DIAL) have been successfully used to detect atmospheric water vapor. System calibration is crucial to ensure that the measured profile accurately represents the concentration profile of atmospheric water vapor. Choosing an effective system calibration method can ensure the accuracy of long‐term lidar measurements. This paper reviews the latest progress and applications of atmospheric water vapor lidar calibration in recent years. The basic principles of Raman lidar and DIAL calibration are introduced. Various methods and benefits of system calibration are discussed. Raman lidar has three commonly used calibration methods: external calibration, internal calibration, and hybrid calibration methods. The most commonly used method is external calibration based on radiosondes. DIAL is usually implemented with an advantageous self‐calibration method. Finally, potential development directions for atmospheric water vapor lidar and calibration technology are discussed.This article is categorized under: Science of Water > Methods Engineering Water > Methods Human Water > Value of Water

Observed humidity trends in dry regions contradict climate models.

Arid and semi-arid regions of the world are particularly vulnerable to greenhouse gas-driven hydroclimate change. Climate models are our primary tool for projecting the future hydroclimate that society in these regions must adapt to, but here, we present a concerning discrepancy between observed and model-based historical hydroclimate trends. Over the arid/semi-arid regions of the world, the predominant signal in all model simulations is an increase in atmospheric water vapor, on average, over the last four decades, in association with the increased water vapor-holding capacity of a warmer atmosphere. In observations, this increase in atmospheric water vapor has not happened, suggesting that the availability of moisture to satisfy the increased atmospheric demand is lower in reality than in models in arid/semi-arid regions. This discrepancy is most clear in locations that are arid/semi-arid year round, but it is also apparent in more humid regions during the most arid months of the year. It indicates a major gap in our understanding and modeling capabilities which could have severe implications for hydroclimate projections, including fire hazard, moving forward.

(Invited) The Internal Oxidation Mechanism of Ti60 Alloy in NaCl-coated Environment at 600o C

When serving in the marine environment, the blades of aircraft engines will suffer serious high-temperature corrosion and their service life will be shortened. This is because the water vapour and salt particles (mainly NaCl) in the marine atmosphere will inevitably be involved in the engine, resulting in severe corrosion of materials. Previous studies on the degradation of titanium alloy under NaCl mainly focused on the active oxidation mechanism, while the mechanism of internal oxidation, which can significantly damage the mechanical properties of the titanium, is not clear. In addition, internal oxidation appears microstructure sensitivity, indicating that microstructure design may be an important way to improve high-temperature corrosion resistance in the marine environment.Consequently, for further understanding the internal oxidation mechanism and the influence of microstructure on corrosion, the composition and morphology of the internal oxidized layer of the Ti60 samples, which corroded with NaCl precoated at 600 oC in moist O2 flow for 100 h, have been studied.According to the results, Ti2O formed within the internal oxidized layer. With the thermodynamic calculation results, this observation proves that internal oxides do not result from the oxidation of metal chlorides. As it is known that titanium has a high affinity to oxygen, the internal matrix turns into titanium oxides with different valence states directly, while TiCl4(g) formed from active oxidation further transports outward and is oxidized at the position with high P(O2).The α secondary phase, located inside the β phase, is more sensitive to NaCl-induced corrosion than the α lamellar outside the β phase. This is because β phase and phase boundaries provide more high-energy channels for corrosive media transport to the α secondary phase, which results in severe loss of metallic elements and oxidation. The design of the α secondary phase may be one essential point for developing titanium alloys with a good combination of mechanical properties and corrosion resistance in marine environments. Figure 1

Revisiting the Link Between Thunderstorms and Upper Tropospheric Water Vapor

AbstractAs the Earth's temperatures continue to rise due to increasing greenhouse gases in the atmosphere, a large portion of the warming is due to positive feedbacks from increasing atmospheric water vapor or specific humidity (SH). Some of this water vapor in the boundary layer is transported via deep convection to the upper troposphere (as droplets and ice crystals), moistening the upper troposphere. These small changes in SH in the upper troposphere have a significant impact on the Earth's radiation balance. We compared global daily lightning from the WWLLN data set, and SH data from the ERA5 reanalysis product for 2019, at a spatial resolution of 5°. Our findings show high spatial and temporal correlations between the lightning activity and the SH concentrations in the upper troposphere. The best correlations (r2 = 0.72, p << 0.001) are between lightning activity and UTWV at the 200 mb level (∼12 km altitude), although the correlations with SH at 300 and 400 mb were only slightly lower. Lightning and SH migrate with the seasons north and south of the equator with both parameters showing maxima in the summer hemisphere around 10° latitude. Furthermore, the correlation increases slightly (r2 = 0.73) if a 1‐day lag is considered between the lightning activity and the UTWV. We find that the daily global SH in the upper troposphere can be best estimated using daily global lightning frequency and a power law having an exponent of 0.33.

Contrasting Seasonal Isotopic Signatures of Near‐Surface Atmospheric Water Vapor in the Central Arctic During the MOSAiC Campaign

AbstractThe Arctic is experiencing unprecedented moistening which is expected to have far‐reaching impact on global climate and weather patterns. However, it remains unclear whether this newly sourced moisture originates locally from ice‐free ocean regions or is advected from lower latitudes. In this study, we use water vapor isotope measurements in combination with trajectory‐based diagnostics and an isotope‐enabled atmosphere general circulation model, to assess seasonal shifts in moisture sources and transport pathways in the Arctic. Continuous measurements of near‐surface vapor, δ18O, and δD were performed onboard RV Polarstern during the Multidisciplinary drifting Observatory for the Study of Arctic Climate expedition from October 2019 to September 2020. Combining this isotope data set with meteorological observations reveals that the spatiotemporal evolution of δ18O mimics changes in local temperature and humidity at synoptic to seasonal time scales, while corresponding d‐excess changes suggest a seasonal shift in the origin of moisture. Simulation results from the particle dispersion model FLEXPART support these findings, indicating that summer moisture originates from nearby open ocean, while winter moisture comes from more remote sources with longer residence time over sea‐ice. Results from a nudged ECHAM6‐wiso simulation also indicate that evaporative processes from the ocean surface reproduce summer isotope values, but are insufficient to explain measured winter isotope values. Our study provides the first isotopic characterization of Central Arctic moisture over the course of an entire year, helping to differentiate the influence of local processes versus large‐scale vapor transport on Arctic moistening. Future process‐based investigations should focus on assessing the non‐equilibrium isotopic fractionation during airmass transformation over sea‐ice.

Severe photochemical pollution formation associated with strong HONO emissions from dew and guttation evaporation

The unknown daytime source of HONO has been extensively investigated due to unexplained atmospheric oxidation capacity and current modelling bias, especially during cold seasons. In this study, abrupt morning increases in atmospheric HONO at a rural site in the North China Plain (NCP) were observed almost on daily basis, which were closely linked to simultaneous rises in atmospheric water vapor content and NH3 concentrations. Dew and guttation water formation was frequently observed on wheat leaves, from which water samples were taken and chemically analyzed for the first time. Results confirmed that such natural processes likely governed the daily nighttime deposition and daytime release of HONO and NH3, which have not been considered in the numerous HONO budget studies investigating its large missing daytime source in the NCP. The dissolved HONO and NH3 in leaf surface water droplets reached 1.4 and 23 mg L−1 during the morning on average, resulting in averaged atmospheric HONO and NH3 increases of 0.89 ± 0.61 and 43.7 ± 29.3 ppb during morning hours, with relative increases of 186 ± 212 % and 233 ± 252 %, respectively. The high atmospheric oxidation capacity contained within HONO was stored in near surface liquid water (such as dew, guttation and soil surface water) during nighttime, which prevented its atmospheric dispersion after sunset and protected it from photodissociation during early morning hours. HONO was released in a blast during later hours with stronger solar radiation, which triggered and then accelerated daytime photochemistry through the rapid photolysis of HONO and subsequent OH production, especially under high RH conditions, forming severe secondary gaseous and particulate pollution. Results of this study demonstrate that global ecosystems might play significant roles in atmospheric photochemistry through nighttime dew formation and guttation processes.

Sensitivity of summer precipitation simulation to the physical parameterizations in WRF over the Tibetan Plateau: A case study of 2018

The Tibetan Plateau (TP) holds a pivotal position in regional and global climate, whereas the atmospheric characteristics vary greatly in the simulation with different physical parameterization schemes at the gray-zone scale (around 9 km). In this study, 24 sets of experiments were set up with different cumulus parameterization schemes (CPSs), microphysics parameterization schemes (MPSs) and planetary boundary layer parameterization schemes (PBLSs) using the WRF model driven by the ERA5 reanalysis to explore the sensitivity and try to summarize a combination of parameterization schemes suitable for the simulation over TP. Based on comparisons against in-situ observations, most CPS experiments showed large wet bias and overestimated occurrence of precipitation events, and CTL without CPS and CU6 with Tiedtke CPS show better performance at gray-zone scale. The influence of MPS and PBLS is less than CPS on the simulation, and Thompson MPS and UW PBLS showed a better performance. Most of the CPS experiments reach an earlier and more intensive peak compared to the Integrated Multi-satellite Retrievals for GPM (IMERG) version 6 satellite precipitation product, except CTL, CU11, and CU6, which show closer but weaker peaks. CPS experiments simulate more precipitation associated with water vapor transporting into TP and anomalous cyclonic circulation against CTL. The less water vapor transport from the south edge of TP in the CTL against CU14, CU16, and CU2, leads to more local precipitation. Graupel particles and the warm-rain process play a crucial role in the precipitation simulation with different MPSs. Although with less water vapor in the low atmosphere, MP2 simulates more precipitation due to more graupel particles and warm-rain processes against CTL. PBLSs have a substantial impact on latent heat, then influence evaporation and precipitation. The lower PBL height usually leads to more latent heat and more precipitation.

Evaluation of the Influence of 2008 Scoping Plan to Carbon Emissions in California by DID

Global warming has been a crucial issue these years as the development of human society and technologies. The main factor is the greenhouse gas emissions, including water vapor, methane, carbon dioxide and nitrous oxide in the earth atmosphere. There are many countries with different kinds of policies to reduce greenhouse gas emissions to slow down the speed of global warming and protect the world environment, such as the California 2008 Scoping Plan. Difference-in-Difference is an estimation method to evaluate the effectiveness of a policy change on a group of individuals. This study selects the transportation sector as the indicator of carbon emissions in California and uses the data from 2004 to 2014 in all 51 states in the U.S. to estimate the influence of 2008 Scoping Plan on carbon emissions in California. The result shows the policy had a positive effect on reducing the carbon emissions in the transportation sector in California, which means that the Scoping Plan is worth continuing to implement and improve to achieve the goal of decreasing greenhouse gas emissions to protect the global environment.

Diurnal variability of atmospheric water vapour, precipitation and cloud top temperature across the global tropics derived from satellite observations and GNSS technique

The diurnal cycle of convection plays an important role in clouds and water vapour distribution across the global tropics. In this study, we utilize integrated moisture derived from the global navigation satellite system (GNSS), satellite precipitation estimates from TRMM and merged infrared dataset to investigate links between variability in tropospheric moisture, clouds development and precipitation at a diurnal time scale. Over 16 years of observations were analysed to estimate the diurnal cycles for 42 sites that span across the global tropics and assess the GNSS precipitable water vapour suitability in tropical moisture variability studies. Results show that the GNSS technique can be successfully used for studies related to the high-resolution temporal variability of integrated atmospheric moisture and, thus, in the analysis of multi-scale interactions and clouds development. For most of the analysed cases, GNSS integrated humidity shows one daily maximum (regardless of the season), which is related to the afternoon precipitation and cloud top temperature daily minimum. Although diurnal integrated moisture variations typically do not exceed 2 mm (usually below 5% of the daily mean value), in favourable large-scale conditions such relatively small changes can lead to the development of convective clouds and can affect precipitation distribution. Thus, GNSS technology allows reliable monitoring of tropospheric moisture variability at a diurnal time scale, which can be leveraged for improved monitoring and prediction of high-impact weather.

On-Orbit Calibration Method for Correction Microwave Radiometer of the HY-2 Satellite Constellation

The HY-2D satellite was successfully launched in 2022, which marks the first phase of the HY-2 satellite constellation. In order to reduce the deviation of wet path delay (WPD) between different satellites in the HY-2 satellite constellation and increase precision in the correction microwave radiometer (CMR) products, on-orbit calibration must be performed to the brightness temperature (BT) of the CMR in this constellation. This study describes the principle and process of on-orbit calibration for CMR in detail. For the three satellites of the HY-2 satellite constellation, after cross-matching with each other within a limited spatio-temporal range, the HY-2B satellite with sounding on the global ocean is selected to the calibration source, calibrating BT from the CMR of the HY-2C and HY-2D satellites to the BT dimension of the HY-2B satellite CMR. To check on-orbit calibration, a retrieval algorithm is built using atmospheric profile data from ECMWF and BT data, obtained from the CMR of the HY-2B satellite; this is used to calculate the atmospheric water vapor (AWV) and WPD from the HY-2 satellite constellation. After on-orbit calibration to the CMRs of the HY-2 satellite constellation, the deviation between the CMR products of different satellites is significantly reduced by over 20%, and the RMS of WPD for the same type of products from the Jason-3 satellite is less than 1 cm. It may be concluded that on-orbit calibration improves the accuracy of AWV and WPD by normalizing the BT dimension for CMRs of the HY-2 satellite constellation, so this calibration method is effective and credible for enhancing the quality of altimeter products in the HY-2 satellite constellation.

A NEW WEATHER FILTER FOR REDUCING WEATHER EFFECT IN CALCULATING SEA ICE CONCENTRATION FROM AMSR2 DATA

Abstract. Ice concentration is one of the most fundamental parameters of sea ice which can be calculated from brightness temperatures measured by passive microwave radiometers such as AMSR2 onboard satellites. However, the presence of atmospheric water vapor, cloud liquid water, etc. is likely to increase the brightness temperatures over open water. As a result, sometimes, certain ice concentrations are calculated over open water covered with heavy clouds. The authors call this kind of area as “false sea ice” and the phenomenon is called the weather effect. In the AMSR2 ice concentration product, a weather filter is used to reduce the weather effect. However, it is known that false sea ice appears occasionally in some areas even in the summertime in AMSR2 ice concentration products. In this study, the authors have modified the original weather filter and added a new weather filter utilizing the following two equations which are TB(23GHzV)<−0.75×(TB(36GHzV)−TB(36GHzH))+253K and TB(36GHzV)−TB(36GHzH) < 57K. If the brightness temperature of the pixel meets the above two equations, we set the ice concentration of the pixel as 0%. By adding the new weather filter, most of the false sea ice that appeared in the ASMR2 ice concentration products could be rejected. JAXA has decided to add this weather filter for producing AMSR2 standard sea ice concentration products.

Global diagnosis of land–atmosphere coupling based on water isotopes

Land–atmosphere coupling (LAC) plays a significant role in weather and climate and is related to droughts and heatwaves. We propose a simple and efficient LAC diagnosis method based on the analysis of water isotopes in atmospheric water vapour and precipitation. Using the method, we identify the primary LAC hotspot regions of the globe and reveal the seasonality of LAC strength. We find that LAC strength exhibits a relationship with latitude. Low latitudes present stronger LAC strength and contribute more significantly to the overall LAC area compared to boreal middle and high latitudes. It's important to note that LAC primarily manifests in the troposphere and is detected in the lower stratosphere of low latitudes, with limited influence observed in the stratosphere. However, the impact of LAC is noticeable in the upper stratosphere in boreal middle and high latitudes. Moreover, the seasonality of LAC strength is pronounced. On a global scale, the season with the strongest LAC is boreal autumn in the Northern Hemisphere but boreal summer in the Southern Hemisphere. Notably, this pattern does not exhibit a seesaw effect between the two hemispheres. Our isotope-based LAC diagnosis method captures the major LAC hotspots found in previous work and validates the seasonality of LAC within these hotspots. This substantiates the reliability and effectiveness of our isotope-based approach.