Influence of water vapor distribution on the simulated track of Typhoon Hato (2017)

Predicting tropical cyclone (TCs) tracks is a primary concern in TC forecasting. Some TCs appear to move in a direction favorable for their development, beyond the influence of the steering flow. Thus, we hypothesize that TCs move toward regions with high water-vapor content in the lower atmosphere. In this study, four numerical experiments, including a control experiment and three sensitivity experiments, were performed using the Weather Research and Forecasting Model, to analyze the relationship between water vapor distribution and the track of Severe Typhoon Hato (2017). Observations validated the features reproduced in the control experiment. The sensitivity experiments were conducted to explore variations in the TC track under different water vapor environments. Results indicate that the horizontal distribution of water-vapor content exerted a greater impact on the TC track than the steering flow when both factors were significant. Further analysis revealed that the TC’s movement vector was between the direction of the steering flow and the direction toward the peak of vorticity increasing area. The peaks of vorticity increasing area were close to the peaks of water vapor increasing area, which also proved the effect of water vapor distribution on the TC track. These results are expected to improve TC track analysis and forecasting.

Gas-Phase Chemical Imaging System by Biofluorometry for Human VOCs Measurement

Many gas-phase biosensors have been developed for human volatiles (acetone, methyl mercaptan, trimethylamine, ethanol, isopropanol, etc.) and for residential harmful VOCs (formaldehyde, toluene, nicotine) causing some diseases. A novel gas-imaging system by biofluorometry with an enzyme immobilized mesh was investigated to demonstrate spatiotemporal gas-imaging for human volatiles (i.e., ethanol and acetaldehyde after drinking). A biofluorometric technique was applied to improve the performance (sensitivity, calibration range, gas-selectivity, etc.) of the gas-imaging system. The biofluorometric sniff-cam for ethanol was fabricated with an ADH (alcohol dehydrogenase) immobilized mesh and an NADH fluorescent visualization unit (UV-LED sheet array and highly sensitive camera); thus, showing the two-dimensional real-time imaging of ethanol vapor distribution (0.5–200 ppm). The system showed rapid and accurate responses and a visible measurement of ethanol in the gas phase. The intensity of fluorescence was linearly related to the concentration of ethanol vapor. The high sensitivity fluorescent imaging of ethanol vapor allows to successfully visualize gaseous ethanol from the human body (exhaled air and skin gas) after drinking. The sniff-cam system would be useful for the conventional detecting and imaging of the volatile biomarkers.

Exploring de formation of the Arsia Mons Elongated Cloud on Mars

<p>In a recent work (Hernández-Bernal et al. 2020) we reported the existence and properties of the AMEC (Arsia Mons Elongated Cloud). This cloud appears every martian year around the southern solstice following a quick daily cycle, it expands up to 1800 km after sunrise and disappears before noon. While in the previous work we made an extensive observational study, a number of questions remain unsolved, including the specific specific set of atmospheric conditions that originates this particular cloud at this moment of the year, and why other near volcanoes do not exhibit analogous clouds. In this work we explore, based on models, the physical conditions of the atmosphere around Arsia Mons, such as temperature gradients, winds, and water vapor distribution, as a first step to try to understand this particular cloud.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.6a91d3aa1fff59104550161/sdaolpUECMynit/12UGE&app=m&a=0&c=8b814a50b210ee1ef3b6c142aecee436&ct=x&pn=gnp.elif&d=1" alt=""></p><p><strong>References</strong>:</p><p>Hernández-Bernal, J., Sánchez-Lavega, A., Río-Gaztelurrutia, T. D., Ravanis, E., Cardesín-Moinelo, A., Connour, K., ... & Hauber, E. An Extremely Elongated Cloud over Arsia Mons Volcano on Mars: I. Life Cycle. Journal of Geophysical Research: Planets, DOI: 10.1029/2020JE006517</p>

Data validation and mesoscale assimilation of Himawari-8 optimal cloud analysis products

Himawari-8 optimal cloud analysis (OCA), which employs all 16 channels of the Advanced Himawari Imager, provides cloud properties such as cloud phase, top pressure, optical thickness, effective radius, and water path. By using OCA, the water vapor distribution can be inferred with high spatiotemporal resolution and with a wide coverage, including over the ocean, which can be useful for improving initial states for prediction of the torrential rainfalls that occur frequently in Japan. OCA products were first evaluated by comparing them with different kinds of data sets (surface, sonde, and ceilometer observations) and with model outputs, to determine their data characteristics. Overall, OCA data were consistent with observations of water clouds with moderate optical thicknesses at low to mid levels. Next, pseudo-relative humidity data were derived from the OCA products, and utilized in assimilation experiments of a few heavy rainfall cases, conducted with the Japan Meteorological Agency’s nonhydrostatic model-based Variational Data Assimilation System. Assimilation of OCA pseudo-relative humidities caused there to be significant differences in the initial conditions of water vapor fields compared to the control, especially where OCA clouds were detected, and their influence lasted relatively long in terms of forecast hours. Impacts of assimilation on other variables, such as wind speed, were also seen. When the OCA data successfully represented low-level inflows from over the ocean, they positively impacted precipitation forecasts at extended forecast times.

Deteksi pengaruh gelombang Kelvin pada fluktuasi uap air di tropopause menggunakan model inversi

Analisis pengaruh gelombang ekuatorial Kelvin terhadap fluktuasi uap air (H2O) di lapisan tropopause (paras tekanan udara 100 hPa), dilakukan dengan memanfaatkan data Microwave Limb Sounder (MLS) Aura versi 4.2 dan angin zonal NCEP DOE Reanalysis II sepanjang tahun 2017. Model inversi gelombang melalui pendekatan Newtonian diterapkan untuk mencari parameter amplitudo (A) dan fasa (φ) gelombang dominan pada variasi anomali H2O (H2O*). Hasil penyelarasan model inversi menunjukkan perambatan H2O* positif ke arah timur bersesuaian dengan angin zonal (U) positif (angin baratan) yang identik dengan pergerakan gelombang Kelvin. Perambatan ini didominasi oleh bilangan gelombang k1 dengan A1 dan φ1 berturut–turut sebesar 0,44 dan 21,1°. Penulis menemukan bahwa variasi uap air dipengaruhi oleh perubahan angin baratan menjadi angin timuran dan konvergensi sebesar 0,15 × 10–5 s–1. Analisis komposit diagram relatif terhadap nilai maksimum H2O* menunjukkan adanya pengaruh gelombang ekuatorial Kelvin terhadap distribusi uap air di tropopause. Penelitian terkait pengembangan model kopel troposfer dan stratosfer perlu mempertimbangkan proses dinamika gelombang Kelvin dan proses radiatif dari konsentrasi uap air di tropopause. Analysis on the influence of equatorial Kelvin wave on the fluctuations in water vapor (H2O) at tropopause (100 hPa air pressure level) has been done utilizing Microwave Limb Sounder (MLS) Aura version 4.2 and zonal wind (U) from NCEP DOE Reanalysis II data throughout the year of 2017. The inverse wave model using Newtonian approximation has been applied to determine the dominant of both wave amplitude (A) and phase (φ) parameters on the H2O anomaly (H2O*). The fitting of inverse modeling result showed an eastward propagation of positive H2O* associated with positive U (westerly wind) which is identical as Kelvin wave movement. The propagation is dominated by wavenumber k1 where A1 and φ1 is 0.44 and is 21.1°, respectively. The authors found that water vapor variations were influenced by the reversal of zonal wind from easterly to easterly and the convergence as large as 0,15 × 10–5 s–1. The composite analysis relative to the maximum value H2O* showed the influence of equatorial Kelvin wave in the water vapor distribution at tropopause. The research on the development of the troposphere –stratosphere coupling model may need to consider the dynamical process of the equatorial Kelvin wave and radiative process of water vapor concentration in the tropopause.

Effects of the Thickness of Boundary Layer on Droplet’s Evaporation Rate

The evaporation rate of a droplet was explained in relation to the thickness of the boundary layer and the condition near the droplet’s surface. However, the number of results obtained from experiments is very limited. This study aims to investigate the thickness of the boundary layer of an ethanol‐water mixture droplet and its effect on the evaporation rate by Z-type Schlieren visualization. Single and double droplets are tested and compared to identify the effect of the second droplet on the average and instantaneous evaporation rate. The double droplet’s lifetime is found to be longer than the single droplet’s lifetime. The formation of a larger vapor region on the top of the droplet indicates a higher instantaneous evaporation rate. The thickness of the boundary layer is found to increase with increase in ethanol concentration. Furthermore, a larger vapor distribution area is found in the case of higher ethanol concentration, which explains the faster evaporation rate at higher ethanol concentration.

Regional Assimilation System for Transformed Retrievals from Satellite High-Resolution Infrared Data

Satellite retrievals strive to exploit the information contained in thousands of channels provided by hyperspectral sensors and show promise in providing a gain in computational efficiency over current radiance assimilation methods by transferring computationally expensive radiative transfer calculations to retrieval providers. This paper describes the implementation of a new approach based on the transformation proposed in 2008 by Migliorini et al., which reduces the impact of the a priori information in the retrievals and generates transformed retrievals (TRs) whose assimilation does not require knowledge of the hyperspectral instruments characteristics. Significantly, the results confirm both the viability of Migliorini’s approach and the possibility of assimilating data from different hyperspectral satellite sensors regardless of the instrument characteristics. The Weather Research and Forecasting (WRF) Model’s Data Assimilation (WRFDA) 3-h cycling system was tested over the central North Pacific Ocean, and the results show that the assimilation of TRs has a greater impact in the characterization of the water vapor distribution than on the temperature field. These results are consistent with the knowledge that temperature field is well constrained by the initial and boundary conditions of the Global Forecast System (GFS), whereas the water vapor distribution is less well constrained in the GFS. While some preliminary results on the comparison between the assimilation with and without TRs in the forecasting system are presented in this paper, additional work remains to explore the impact of the new assimilation approach on forecasts and will be provided in a follow-up publication.

The vertical structure and spatial variability of lower-tropospheric water vapor and clouds in the trades

Horizontal and vertical variability of water vapor is omnipresent in the tropics, but its interaction with cloudiness poses challenges for weather and climate models. In this study we compare airborne lidar measurements from a summer and a winter field campaign in the tropical Atlantic with high-resolution simulations to analyze the water vapor distributions in the trade wind regime, its covariation with cloudiness, and their representation in simulations. Across model grid spacing from 300 m to 2.5 km, the simulations show good skill in reproducing the water vapor distribution in the trades as measured by the lidar. An exception to this is a pronounced moist model bias at the top of the shallow cumulus layer in the dry winter season which is accompanied by a humidity gradient that is too weak at the inversion near the cloud top. The model's underestimation of water vapor variability in the cloud and subcloud layer occurs in both seasons but is less pronounced than the moist model bias at the inversion. Despite the model's insensitivity to resolution from hecto- to kilometer scale for the distribution of water vapor, cloud fraction decreases strongly with increasing model resolution and is not converged at hectometer grid spacing. The observed cloud deepening with increasing water vapor path is captured well across model resolution, but the concurrent transition from cloud-free to low cloud fraction is better represented at hectometer resolution. In particular, in the wet summer season the simulations with kilometer-scale resolution overestimate the observed cloud fraction near the inversion but lack condensate near the observed cloud base. This illustrates how a model's ability to properly capture the water vapor distribution does not necessarily translate into an adequate representation of shallow cumulus clouds that live at the tail of the water vapor distribution.