Relative Humidity Profiles Research Articles

Multiwavelength Raman lidar system for profiling the CCN number concentrations

Cloud condensation nuclei (CCN) play an important role in the research of cloud microphysical and aerosol–cloud interactions. This study employs a multiwavelength Raman lidar for measuring CCN concentration. First, the multiwavelength Raman lidar was used to measure the atmospheric relative humidity profile, and the combination of relative humidity and the aerosol backscattering coefficient was used to retrieve the hygroscopic growth factor. By fitting the hygroscopic growth factor using the κkappa parameter model, the hygroscopic parameter κkappa that characterizes the hygroscopicity of aerosols was obtained. Then, the critical activation radius of aerosols was derived using the κ–Köhler theory and hygroscopicity parameter κkappa. Finally, the CCN number concentration was obtained by combining with the aerosol particle size distribution. Experiments were conducted to verify the feasibility of the multiwavelength Raman lidar. Results showed that the effective detection range of the lidar is approximately 0–4 km. The error of the temperature measured by the lidar at the height of 0.3–3.8 km is approximately ±1K. When the relative humidity change is 0.77–0.87, the range of the hygroscopic growth factor change is 1.06–1.10, the hygroscopic parameter γ is 0.065, and the hygroscopic parameter κkappa is 0.009. The CCN numbers concentration decreases with height but increases closer to the cloud. The multiwavelength Raman lidar is an important tool for detection of cloud microphysical and aerosol–cloud interactions and could have scientific importance and research value, both for improved understanding of the formation of clouds and precipitation and for enhanced accuracy of weather modification.

Improving Atmospheric Temperature and Relative Humidity Profiles Retrieval Based on Ground-Based Multichannel Microwave Radiometer and Millimeter-Wave Cloud Radar

Obtaining temperature and humidity profiles with high vertical resolution is essential for describing and predicting atmospheric motion, and, in particular, for understanding the evolution of medium- and small-scale weather processes, making short-range and near-term weather forecasting, and implementing weather modifications (artificial rainfall, artificial rain elimination, etc.). Ground-based microwave radiometers can acquire vertical tropospheric atmospheric data with high temporal and spatial resolution. However, the accuracy of temperature and relative humidity retrieval is still not as accurate as that of radiosonde data, especially in cloudy conditions. Therefore, improving the observation and retrieval accuracy is a major challenge in current research. The focus of this study was to further improve the accuracy of atmospheric temperature and humidity profile retrieval and investigate the specific effects of cloud information (cloud-base height and cloud thickness) on temperature and humidity profile retrieval. The observation data from the ground-based multichannel microwave radiometer (GMR) and the millimeter-wave cloud radar (MWCR) were incorporated into the retrieval process of the atmospheric temperature and relative humidity profiles. The retrieval was performed using the backpropagation neural network (BPNN). The retrieval results were quantified using the mean absolute error (MAE) and root mean square error (RMSE). The statistical results showed that the temperature profiles were less affected by the cloud information compared with the relative humidity profiles. Cloud thickness was the main factor affecting the retrieval of relative humidity profiles, and the retrieval with cloud information was the best retrieval method. Compared with the retrieval profiles without cloud information, the MAE and RMSE values of most of the altitude layers were reduced to different degrees after adding cloud information, and the relative humidity (RH) errors of some altitude layers were reduced by approximately 50%. The maximum reduction in the RMSE and MAE values for the retrieval of temperature profiles with cloud information was about 1.0 °C around 7.75 km, and the maximum reduction in RMSE and MAE values for the relative humidity profiles was about 10%, which was obtained around 2 km.

Determination of Variable Humidity Profile for Lactic Acid Maximization in Fungal Solid-State Fermentation

Solid-state fermentation (SSF) is the bioprocess where microorganisms are cultivated in the absence of free water under controlled conditions. Lactic acid can be produced by Rhizopus oryzae SSF of grape stalks. During the microorganism’s growth, the temperature and water content of the solid bed fluctuate, leading to areas of either dry or excessive moisture in the solid substrate. Therefore, it is crucial to control the water supply to the matrix. In this work, we obtain lactic acid through SSF of grape stalks using Rhizopus oryzae NCIM 1299. The SSF was conducted at a fixed temperature of 35 °C, with five constant relative humidity (RH) levels: 50, 57, 65, 72, and 80%RH. Mathematical models, including the Logistic and First-Order Plus Dead-Time models for fungal biomass growth and the Luedeking and Piret with Delay Time model for lactic acid production, were adjusted to kinetic curves. Growth kinetic parameters (Xmax, μmax, Tp, T0, Yp/x, and td) were determined for all conditions. These kinetic parameters were then correlated with relative humidity using a second-degree polynomial relationship. We observed a decrease in Xmax with an increasing %RH, while the value of Yp/x increased at a higher %RH. Finally, the optimal variable relative humidity profile was obtained by applying the dynamic optimization technique, resulting in a 16.63% increase in lactic acid production.

Raindrop size distribution characteristics of pre-monsoon precipitation observed over eastern India

The knowledge of raindrop size distribution (DSD) is crucial for understanding the microphysical processes involved with the precipitation. Different empirical relationships established with DSD parameters, like radar reflectivity– rainfall rate (Z–R) relationships and shape–slope (μ–Ʌ) relationships, can progress the rainfall estimation algorithms and cloud modeling simulations. In the present study, long-term (2018–2021) measurements of a Laser Precipitation Monitor (LPM) disdrometer installed at the National Institute of Technology, Rourkela, India is used to investigate the DSD characteristics of pre-monsoon (March–May) rainfall. Along with the disdrometer data, auxiliary parameters like convective available potential energy (CAPE), total column water vapor (TCWV), vertical profiles of temperature and relative humidity from reanalysis data sets of ECMWF (European Centre for Medium-Range Weather Forecasts) fifth-generation reanalysis (ERA5) are also used in this study. Based on standardized rainfall anomaly, the pre-monsoon precipitation days are classified into strong, moderate, and weak rainy days, and they contributed to 58.69%, 32.7%, and 8.61% of total rainfall, respectively. The average DSD indicated noteworthy variations among strong, moderate, and weak rainy days with maximum (minimum) concentration of raindrops in strong (weak) rainy days. The mean value of rain rate (R), normalized intercept parameter (Nw), and mass-weighted mean diameter (Dm) is maximum during days of strong rainfall. Strong rainy days showed high-value CAPE, TCWV and vertical profile of relative humidity. The majority of R is contributed by moderate-sized raindrops with a significant difference in the Z–R and μ–Λ relationships among three types of rainy days.

Development of Accelerated Durability Test Protocols for Polymer Electrolyte Membrane Fuel Cell Stacks Under Realistic Operating Conditions

ABSTRACTPolymer electrolyte membrane fuel cell durability is still a major challenge. To overcome time‐consuming durability tests, so‐called accelerated durability tests (ADTs) are of urgent need. This work presents our recent results in developing ADT protocols in the context of realistic operating conditions, especially voltage clipping at 0.85 V. A 5500 h long‐term test was carried out as a reference applying a realistic automotive drive cycle. Focusing on different stressors such as temperature, relative humidity (RH), and load profile four different ADT protocols of 1200 h duration were derived. Seven‐cell short stacks with 240 cm2 active area were used. Comparing cell voltage as a key indicator, an acceleration factor of 3–7 could be achieved. In‐situ characterization techniques such as spatially resolved current measurement, cyclic voltammetry, and electrochemical impedance spectra were employed to investigate the influences of individual stressors on specific degradation mechanisms and components. The highest acceleration was observed in the mass transport region of ADTs addressing RH as a stressor, suggesting that RH cycling leads to increased degradation of hydrophobic surfaces. Increased temperature was found to accelerate primarily carbon support degradation. Accelerated catalyst aging seems to be low, demonstrating the effectiveness of voltage‐clipping conditions. Our most promising ADT shows quite a homogeneous acceleration of voltage degradation across all current regions.

Spatially distributed atmospheric boundary layer properties in Houston – A value-added observational dataset

In 2022, Houston, TX became a nexus for field campaigns aiming to further our understanding of the feedbacks between convective clouds, aerosols and atmospheric boundary layer (ABL) properties. Houston’s proximity to the Gulf of Mexico and Galveston Bay motivated the collection of spatially distributed observations to disentangle coastal and urban processes. This paper presents a value-added ABL dataset derived from observations collected by eight research teams over 46 days between 2 June - 18 September 2022. The dataset spans 14 sites distributed within a ~80-km radius around Houston. Measurements from three types of instruments are analyzed to objectively provide estimates of nine ABL parameters, both thermodynamic (potential temperature, and relative humidity profiles and thermodynamic ABL depth) and dynamic (horizontal wind speed and direction, mean vertical velocity, updraft and downdraft speed profiles, and dynamical ABL depth). Contextual information about cloud occurrence is also provided. The dataset is prepared on a uniform time-height grid of 1 h and 30 m resolution to facilitate its use as a benchmark for forthcoming numerical simulations and the fundamental study of atmospheric processes.

Hygrothermal response to air movements in wall junctions: Comparison between two numerical approaches and experiments

Airflow in wall-to-wall junctions is known to have a major hygrothermal impact on building performance. However, current and validated modeling options to simulate such phenomena are limited. This paper develops and compares two numerical models to study the heat and moisture transfer due to air infiltrations through a prefabricated wall-to-wall junction. The first model explicitly accounts for the airflow with a pipe flow approach. The second model is a modification to a typical approach to simulate ventilated cavities in building envelope simulation tools and mimics the effect of the airflow through source terms. Both approaches were introduced in a heat and moisture transfer 2D finite element model. Additionally, laboratory measurements were conducted in a climatic chamber to validate the simulation results. Six scenarios were tested experimentally under steady-state conditions. These datasets were used to calibrate different parameters of the models, such as material properties, the junction air gap thickness, and the magnitude of the heat and moisture source terms. Both sets of numerical results provided reasonable agreement with the measurements. The first approach outputs more accurate temperature and relative humidity values than the second one. However, considering uncertainties, no method predicted a perfect fit with the relative humidity profiles. Close to the junction, the first method estimates better the relative humidity than the second one. This work provides guidelines to better model and account for wall junctions in building envelope simulators.

Modelling atmospheric behaviour over southern West Africa using RegCM 4.7.1: Case assessment of relative humidity and zonal wind profiles based on the 2016 DACCIWA summertime field campaign

In this paper, we present an analysis of summertime atmospheric simulation (June–July 2016) for southern West Africa (sWA) using the RegCM 4.7.1 regional climate model to describe the atmospheric behaviour over the region, and also engage comparisons between the modelled data and observed upper air data acquired during the DACCIWA (Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa) field campaign period. First, assessments of relative humidity and zonal wind profiles were made for selected coastal and inland stations, to infer the relative vertical and temporal atmospheric differences for both locations. Thereafter, the model’s performance was evaluated, capturing an excessive wet bias in RH profiles of the model with accompanying reduced zonal winds at the Tropical Easterly Jet (TEJ) region and thus produces excessive upper tropospheric cloud liquid water content. Also, in the lower troposphere (particularly, the monsoon layer), RegCM 4.7.1 model captures adequate spatial differences in both RH and zonal wind profiles along the coast and inland. We judge this outcome to be a valuable contribution on the path to rendering RegCM4 a good tool for simulating atmospheric and climate dynamics in sWA.

Aerodynamic properties of boundary layers along the roof of a large banana screenhouse under near-neutral atmospheric stability

Cultivation under screens and in screenhouses protects the crops from insects and extreme climate conditions and allows water saving. Previous studies considered the aerodynamic properties of boundary layers along two types of screens: a small shading thermal screen covering a hedgerow citrus orchard and a large 50-mesh, insect-proof screen covering a pepper plantation. To extend the previous results, a third type of screen was analysed in this study, a large flat-roof 17-mesh white woven shading screen covering a banana plantation. Vertical profiles of wind speed, air temperature, relative humidity, and friction velocity were measured by a lifting tower, and wind profiles were analysed under near-neutral atmospheric stability. Results show that normalised friction velocity, normalised roughness length, normalised zero plane displacement height and aerodynamic resistance are closer to the previous results of the large insect-proof screenhouse than those of the small shade net.

Wind Profile Retrieval Based on LSTM Algorithm and Mobile Observation of Brightness Temperature over the Tibetan Plateau

Stationary or mobile microwave radiometers (MRs) can measure atmospheric temperature, relative humidity, and water vapor density profiles with high spatio-temporal resolution, but cannot obtain the vertical variations of wind field. Based on a dataset of brightness temperatures (TBs) measured with a mobile MR over the Three-River-Source Region of the Tibetan Plateau from 18 to 30 July 2021, we develop a direct retrieval method for the wind profile (WP) based on the Long Short-Term Memory (LSTM) network technique, and obtain the reliable dynamic variation characteristics of the WP in the region. Furthermore, the ground-based radiative transfer model for TOVS (RTTOV-gb) was employed to validate the reliability of the TB observation, and we analyzed the impact of weather conditions, altitude, observational mode, and TB diurnal variation on the accuracy of the TB measurement and the retrieval of the WP. Results show that the TB from the mobile observation (MOTB) on clear and cloudy days are close to those of the simulated TB with the RTTOV-gb model, while TB measurements on rainy days are far larger than the modeled TBs. When compared with radiosonde observations, the WPs retrieved with the LSTM algorithm are better than the ERA5 reanalysis data, especially below 350 hPa, where the root mean square errors for both wind speed and wind direction are smaller than those of ERA5. The major factors influencing WP retrieval include the weather conditions, altitude, observational mode, and TB diurnal variation. Under clear-sky and cloudy conditions, the LSTM retrieval method can reproduce the spatio-temporal evolution of wind field and vertical wind shear characteristics. The findings of this study help to improve our understanding of meso-scale atmospheric dynamic structures, characteristics of vertical wind shear, atmospheric boundary layer turbulence, and enhance the assessment and forecasting accuracy of wind energy resources.

Improvement of Stable Atmospheric Boundary Simulation with High-Spatiotemporal-Resolution Nudging over the North China Plain

The WRF model often struggles to accurately replicate specific characteristics of the atmospheric boundary layer, particularly under highly stable conditions. In this study, we reconstructed an OBS-nudging module using meteorological data with high spatiotemporal resolution, then coupled it in the WRF model (WRF-OBS) to improve stable boundary layer (SBL) simulation over the North China Plain (NCP). The results showed that WRF-OBS improved the simulation of SBL characteristics and reduced the deviation from observations significantly. The correlations (R2) between WRF-OBS simulations and observations of 2 m temperature, relative humidity, and 10 m wind speed at 460 stations across the NCP were 0.72, 0.56, and 0.75, respectively, which were much higher than the values for results from the unassimilated WRF model (WRF-BS). The simulated vertical profiles of temperature, relative humidity, and wind were generally consistent with observations at Pingyuan station. The meteorological factors which caused heavy air pollution was also investigated based on WRF-OBS simulation. The SBL characteristics obtained from WRF-OBS showed that light wind persisted over the NCP region during the period of heavy pollution, and Pingyuan was affected by warm and humid air. Vertically, the persistent temperature inversion at Pingyuan station was one of the main drivers of the heavy pollution. The WRF-OBS simulation captured the characteristics of the two temperature inversion layers very well. The two inversion layers covered the NCP, with a horizontal scale of approximately 200 km, and created very stable conditions, preventing the vertical diffusion of pollutants and maintaining high PM2.5 concentrations.

An Analytic Theory of Near-Surface Relative Humidity over Land

Abstract There is no simple explanation for the spatial structure of near-surface relative humidity over land. We present a diagnostic theory for zonally and temporally averaged near-surface relative humidity (RH) over land based on energy budgets of an atmospheric column in radiative–convective equilibrium. The theory analytically relates RH to the surface evaporative fraction (EF), has no calibrated parameters, and is quantitatively accurate when compared with RH from a reanalysis, and with cloud-permitting simulations over an idealized land surface. The theory is used to answer two basic questions. First, why is RH never especially low (e.g., 1%)? The theory shows that established lower bounds on EF over land and ocean are equivalent to lower bounds on RH that preclude particularly low values, at least for conditions typical of the modern Earth. Second, why is the latitudinal profile of RH over land shaped like the letter W, when both specific humidity and saturation specific humidity essentially decline monotonically from the equator to the poles? The theory predicts that the latitudinal profile of RH should look more like that of water stored in the soil (which also exhibits a W-shaped profile) than in the air (which does not).

Enhanced prediction of premonsoon thunderstorms over eastern India through assimilation of INSAT‐3D sounding data

AbstractThe present study assesses the impact of Indian National Satellite 3D (INSAT‐3D)‐derived atmospheric (temperature and relative humidity) profiles on the simulation of severe thunderstorms over eastern India during the premonsoon season. Two sets of numerical experiments, without assimilation (CNTL) and with assimilation of INSAT‐3D profiles (INSAT) have been conducted using the three‐dimensional variational data assimilation system of the Weather Research and Forecasting model for 11 thunderstorm events. Analysis increments are positive with INSAT profile assimilation in the lower to middle atmosphere in the thunderstorm region. The errors in the initial fields have been reduced by approx. 50% after the assimilation. After assimilation, the predictions of the surface fields (2‐m temperature, 2‐m relative humidity, and 10‐m wind speed) have been improved at the mature stage (by 37%, 26%, and 15%) compared to the CNTL. Similar improvements are noticed in the vertical profiles of relative humidity and wind speed in the INSAT experiment. The time and magnitude of updrafts and downdrafts improved in INSAT. After assimilation, rainfall intensity improved in nine cases, and time improved in four cases out of 11. The Critical Success Index (False Alarm Rate) of the INSAT ranges from approx. 0.6–0.15 (∼0.37–0.48) for all thresholds, and are higher (lower) than the CNTL. The rainfall area is improved by 25% for light rainfall, 11% for moderate rainfall, and 2% for heavy rainfall in the INSAT over the CNTL experiment. Overall thunderstorm prediction has been improved with the assimilation of INSAT‐3D data. Thus, the study highlights the viability of INSAT‐3D profiles in improving thunderstorm predictions over eastern India.

Performance of Clusterbean (Cyamopsis tetragonoloba L.) Varieties under Different Temperature and Relative Humidity Profiles

A study was performed at Department of Plant Pathology during year 2020, CCS Haryana Agricultural University to find the effect of different growing environments on temperature and humidity profile development, yield and its attributes in clusterbean crop. Three varieties of clusterbean varieties i.e. HG 365 (V1), HG 563 (V2) and HG 2-20 (V3) with each sown at three different dates of sowing i.e first (D1), third (D2) and fourth (D4) week of July in factorial randomized block design and replicated thrice. The diurnal range of temperature profiles at the emergence stage and flowering stage were higher in the crop sown in the first fortnight of July as compared to the second and third fortnights of July. Crops sown in the fourth week of July had a greater diurnal range of relative humidity profiles at the vegetative and pod formation stage while at flowering stage higher diurnal variation were present in first week of July sown crop. However, among different cultivars of clusterbean, no variation in temperature and humidity profile were observed. Significantly higher number of branches per plant, number of pods per plant, pod length, number of seeds per pod, harvesting index, grain and straw yield were found in D1 (first week of July) and V2 (HG 563) as compared to remaining dates of sowing and varieties, respectively.

Theoretical model for the coupling effect of moisture transport on chloride penetration in concrete

Concrete's internal pore structure crucially influences the rate at which moisture and chemicals, e.g., chloride, move through concrete. This paper explores the coupling effect of moisture transport on the chloride penetration in both saturated and non-saturated concrete, which arises because moisture carries chloride ions as it moves through the pores. To characterize simultaneous moisture and chloride movement in general, a modified Fick's first law can be used for the flux of chloride ions as well as the flux of moisture. A mathematical model is developed based on a multiscale approach for the effective humidity diffusion coefficient, accounting for different moisture diffusion mechanisms in different sizes of pores: Molecular, Knudsen, and Surface diffusions. Based on the results for humidity diffusion coefficient, a material model for the coupling parameter was developed. Validation based on available experimental results demonstrated excellent agreement in predicting pore relative humidity and chloride content profiles.

An Online Assimilation Method to Improve the Numerical Forecast of Sea Fog Using Microwave Radiometer‐Retrieved Cloud Water Path

AbstractNumerical forecast of the sea fog is sensitive to the initial moist stratification within the marine atmospheric boundary layer (MABL). This study develops an online assimilation method to improve the MABL thermal and moist structures in sea fog ensemble forecasts based on the Weather Research and Forecasting model and Grid‐point Statistical Interpolation/EnKF system. It uses the satellite‐retrieved cloud water path (CWP) as the indicator of sea fog and low‐level stratus to determine the best ensemble members at each grid point. The relative humidity and cloud water profiles are extracted from the best members to generate a series of pseudo‐observations, which are assimilated to update all the members by EnKF method. The new method significantly improves the ensemble forecast of five widespread advection fog events over the Yellow Sea, which can be attributed to the decrease of both missed and spurious fog areas. The case study shows that assimilating the information of both humidity and cloud water outperforms assimilating either of them, while the impact of directly assimilating CWP observation is insignificant. The analysis increments of cloud water, thermal and moist structures in MABL together contribute to the correction of forecasted sea fog. The generation of pseudo‐observations can use the dynamic compatibility of the model to alleviate the impact of erroneous data in the observation, leading to the low sensitivity of the new method to CWP retrieval error.

Control of Stability and Relative Humidity in the Radiative‐Convective Equilibrium Model Intercomparison Project

AbstractThe Radiative‐Convective Equilibrium Model Intercomparison Project (RCEMIP) exhibits a large spread in the simulated climate across models, including in profiles of buoyancy and relative humidity. Here we use simple theory to understand the control of stability, relative humidity, and their responses to warming. Across the RCEMIP ensemble, temperature profiles are systematically cooler than a moist adiabat, and convective available potential energy (CAPE) increases with warming at a rate greater than that expected from the Clausius‐Clapeyron relation. There is higher CAPE (greater instability) in models that are on average moister in the lower‐troposphere. To more explicitly evaluate the drivers of the intermodel spread, we use simple theory to estimate values of entrainment and precipitation efficiency (PE) given the simulated values of CAPE and lower‐tropospheric relative humidity. We then decompose the intermodel spread in CAPE and relative humidity (and their responses to warming) into contributions from variability in entrainment, PE, the temperature of the convecting top, and the inverse water vapor scale height. Model‐to‐model variation in entrainment is a dominant source of intermodel spread in CAPE and its changes with warming, while variation in PE is the dominant source of intermodel spread in relative humidity. We also decompose the magnitude of the CAPE increase with warming and find that atmospheric warming itself contributes most strongly to the CAPE increase, but the indirect effect of increases in the water vapor scale height with warming also contribute to increasing CAPE beyond that expected from Clausius‐Clapeyron.

Drying model based on the relative humidity profile of thin-layer tomatoes in an indirect solar dryer

This work defined the development of a model for thin-film drying of tomatoes using an indi-rect solar dryer. Drying experiments were carried out and the drying model was approximated by a simplified model determined by the measurements collected during the experiments, in particular, the measurement of the relative humidity of the tomato during two days of drying coupled with the thermal behaviour of the drying device in free convection. The results show that with good measurements, it is possible to approximate the drying characteristic curve by a linear model with very high statistical performance indicators. The experiments also show that depending on the drying process adopted, the water behaviour of the tomato can change. In addition, the thin-film drying model adopted made it possible to assess the solar drying kinetics of the tomato variety studied. The results obtained finally show that the dryness of the tomato is reached after about 14 hours of drying. The drying temperature reaches an average of 80°C, and the final product water content after the optimal drying time is about 0.40 kg.water/kg.ms on a dry basis. At the end of this study, we concluded that the drying air temperature represents the most important parameter affecting the drying kinetics. The very good agreement between the experimental and numerical results obtained shows that the theoretical model and assumptions used are acceptable, and that our calculation model is reliable.

Characteristics of atmospheric variables over the southern coast of West Java in the presence of Australian Monsoon and MRG waves

The characteristics of atmospheric variables over the southern coast of West Java in the presence of Australian Monsoon (AUM) and Mixed Rossby-Gravity (MRG) waves were investigated by conducting a dedicated radiosonde observation campaign from 26 to 29 September 2022 at Pameungpeuk Station (107.7°E, 7.6°S). The vertical profiles of pressure, temperature, relative humidity, and wind in the presence of the AUM and MRG waves were obtained and analyzed. The Global Navigation Satellite System - Radio Occultation (GNSS-RO) and the latest ECMWF climate reanalysis (ERA5) data were used to identify the MRG waves features using Hovmöller, space-time spectral, and wavelet analyses. Furthermore, spatial and time-series analyses were performed to study the wave propagation. The results showed the characteristics of atmospheric variables over Pameungpeuk Station in the presence of the AUM and MRG waves. We found that the presence of AUM significantly reduced the relative humidity, particularly in the region from 2 to 10 km altitude, and enhanced the average wind speed during the campaign compared to the wet season. Moreover, we found the reduction of low-level pressure, the enhancement of temperature and relative humidity in the mid-troposphere, and the weakening of the easterly and southerly winds during the dry phase approaching the wet phase of the MRG waves over the southern coast of West Java following the wave structure and propagation.

Sensitivity of cirrus and contrail radiative effect on cloud microphysical and environmental parameters

Abstract. Natural cirrus clouds and contrails cover about 30 % of the Earth's mid-latitudes and up to 70 % of the tropics. Due to their widespread occurrence, cirrus clouds have a considerable impact on the Earth energy budget, which, on average, leads to a warming net radiative effect (solar + thermal infrared). However, whether the instantaneous radiative effect (RE), which in some cases corresponds to a radiative forcing, of natural cirrus or contrails is positive or negative depends on their microphysical, macrophysical, and optical properties, as well as the radiative properties of the environment. This is further complicated by the fact that the actual ice crystal shape is often unknown, and thus, ice clouds remain one of the components that are least understood in the Earth's radiative budget. The present study aims to investigate the dependency of the effect on cirrus RE on eight parameters, namely solar zenith angle, ice water content, ice crystal effective radius, cirrus temperature, surface albedo, surface temperature, cloud optical thickness of an underlying liquid water cloud, and three ice crystal shapes. In total, 283 500 plane-parallel radiative transfer simulations have been performed, not including three-dimensional scattering effects. Parameter ranges are selected that are typically associated with natural cirrus and contrails. In addition, the effect of variations in the relative humidity profile and the ice cloud geometric thickness have been investigated for a sub-set of the simulations. The multi-dimensionality and complexity of the eight-dimensional parameter space makes it impractical to discuss all potential configurations in detail. Therefore, specific cases are selected and discussed. For a given parameter combination, the largest impact on solar, thermal-infrared (TIR), and net RE is related to the ice crystal effective radius. The second most important parameter is ice water content, which equally impacts the solar and terrestrial RE. The solar RE of cirrus is also determined by solar zenith angle, surface albedo, liquid cloud optical thickness, and ice crystal shape (in descending priority). RE in the TIR spectrum is dominated by surface temperature, ice cloud temperature, liquid water cloud optical thickness, and ice crystal shape. Net RE is controlled by surface albedo, solar zenith angle, and surface temperature in decreasing importance. The relative importance of the studied parameters differs, depending on the ambient conditions. Furthermore, and during nighttime the net RE is equal to the TIR RE. The data set generated in this work is publicly available. It can be used as a lookup table to extract the RE of cirrus clouds, contrails, and contrail cirrus instead of full radiative transfer calculations.