Will it be duststorm or thunderstorm today ?

ABSTRACT. Attempt to develop a distinct technique for the prediction of duststorm or duststorm followed by thundershower during pre-monsoon season over Gwalior, has been made, Two mean 0000 UTC tephigrams have been produced for the days when the duststorms and thunderstorms occurred. Difference is highlighted in the 0000 UTC surface and TEMP data on the days of duststorm/duststorm followed by thundershower with those on the days of thunderstorm. Statistical analysis of the duststorm data over Gwalior has also been carried out with respect to direction, time, fortnight and month of occurrence of the event. For prediction of peak gust speed (PGS) of squall due to duststorm a single regression equation has been developed.

Hydrological and Meteorological Controls on Large Wildfire Ignition and Burned Area in Northern California during 2017–2020

This study examined the hydrological/meteorological controls on large wildfires > 10,000 acres (40.5 km2) during 2017–2020 in Northern California at spatial and temporal scales of the target wildfires’ occurrence or growth. This study used the following simple indices for analysis: Moisture Deficit Index (MDI) computed by dividing vapor pressure deficit by soil moisture, MDIWIND computed by multiplying MDI by horizontal wind speed, and MDIGUST computed by multiplying MDI by wind gust speed. The ignition location MDIWIND and MDIGUST showed larger values on the ignition date in fire-years compared to non-fire-years for most of the target wildfires (95.8% and 91.7%, respectively). The peak timing of MDIGUST, which is to evaluate the integrated effect of dry atmosphere/soil and windy condition, coincided with the ignition date for August Complex Fire 2020, Ranch Fire 2018, Claremont-Bear Fire 2020, and Camp Fire 2018. We also found that August Complex Fire 2020, Claremont-Bear Fire 2020, and Camp Fire 2018 occurred in the areas where MDIGUST became spatially and temporally high. Further, strong relationships were found between burned area sizes of the target wildfires and MDI (R = 0.62, p = 0.002), MDIWIND (R = 0.72, p < 0.001), and MDIGUST (R = 0.68, p < 0.001). Overall, the findings in this study implied the strong effect of dry atmosphere/soil and windy conditions on recent large wildfire activities in Northern California. The findings could contribute to a more temporally and spatially detailed forecast of wildfire risks or a better understanding of wildfires’ occurrence and growth mechanisms.

Damages Scale as a Supporting Tool for Windstorm Early Warning System in Malaysia

It is a fact that windstorm is a natural disaster that can create enormous damages. Thus, the article aims to serve as a guideline in establishing the damages scale as the supporting tool in the windstorm disaster management. The purpose of the scale is to mitigate impacts of windstorm via early warning system, so that local authorities and public at the affected area are able to know the worst-case scenario if windstorm occurred and could make early preparation in minimising the impacts. The damage scale is established based on the current damage criteria as an early warning of windstorm occurrences was adopted from the damages scale which was established outside Malaysia. On the other hand, there is no damages scale originally established in the country. In order to establish this supporting tool, 51 windstorm occurrences in year 2012 to 2016 from 6 districts in Peninsular Malaysia were selected as a study case and 246 damages were assessed. Besides windstorm damages, gust speed, wind direction, rainfall and radar images as raw data, the study also acquires local conditions wind multiplier map coordinated with meteorological station and overlaid with wind direction map at the study area as well. All the damage locations for each windstorm occurrence will be coordinated in the local conditions wind multiplier map. However, the damages which located underneath the same convective cluster with meteorological station, in position with wind direction and gust speed greater than hazard threshold only will be determined its associated intensity. The scale listed each potential damage according to categories either building, property, or tree. The gust speeds at 1-minute in the scale are between 9.0 m/s to 19.3 m/s. From the study, damages scale has similar hierarchy of level damages with existing damages scale but much lower intensity.

Atmospheric Resuspension of Insoluble Radioactive Cesium Particles Found in the Difficult-to-Return Area in Fukushima

The deposition of insoluble radiocesium bearing microparticles (CsMPs), which were released from the Fukushima Daiichi Nuclear Power Plant (F1NPP) accident in March 2011, has resulted in the widespread contamination of eastern Japan. Obviously, these deposited insoluble CsMPs may become the secondary contamination sources by atmospheric migration or other environmental transferring process, however, the understanding of the transport mechanism remains non-elucidation, and the relevant evidence has not been directly provided. This study, for the first time, provides the direct evidence for the resuspension of these insoluble CsMPs to the atmosphere from 1) proximity of 137Cs radioactivity and resemblance of the morphology and the elemental compositions of CsMPs in the samples of soil and aerosol derived from the same sampling site, 2) the special characteristics of the resuspended CsMPs of which the ratios of Na/Si, K/Si and/or Cs/Si were smaller than those from the initially released CsMPs collected at either long distance or near F1NPP, which can be ascribed to the slowly natural corrosion of CsMPs by the loss of the small amount of soluble contents in CsMPs and 3) high CsMPs concentration of 10 granules/gram in the surface soil of our sampling site and the observed resuspension of surface soil dust at wind gust speed higher than 4 m s-1. Specifically, fifteen single CsMPs were successfully isolated from the aerosol filters collected by unmanned high-volume air samplers at a severely polluted area in Fukushima Prefecture, about 25 km away from F1NPP, from January 2015 to September 2019. The mean diameter of these CsMPs was 1.8 ± 0.5 μm, and the average 137Cs radioactivity was 0.35 ± 0.23 Bq/granule. The contribution rate of the resuspended CsMPs to the atmospheric radiocesium was estimated from the ratio of 137Cs radioactivity of a single CsMP to that of the aerosol filter to be of 23.9 ± 15.3%. There has been no considerable decreasing trend in the annual CsMP resuspension frequency.

Tropical cyclone simulations over Bangladesh at convection permitting 4.4 km & 1.5 km resolution

High resolution simulations at 4.4 km and 1.5 km resolution have been performed for 12 historical tropical cyclones impacting Bangladesh. We use the European Centre for Medium-Range Weather Forecasting 5th generation Re-Analysis (ERA5) to provide a 9-member ensemble of initial and boundary conditions for the regional configuration of the Met Office Unified Model. The simulations are compared to the original ERA5 data and the International Best Track Archive for Climate Stewardship (IBTrACS) tropical cyclone database for wind speed, gust speed and mean sea-level pressure. The 4.4 km simulations show a typical increase in peak gust speed of 41 to 118 knots relative to ERA5, and a deepening of minimum mean sea-level pressure of up to −27 hPa, relative to ERA5 and IBTrACS data. The downscaled simulations compare more favourably with IBTrACS data than the ERA5 data suggesting tropical cyclone hazards in the ERA5 deterministic output may be underestimated. The dataset is freely available from 10.5281/zenodo.3600201.

Historical Winter Storm Atlas for Germany (GeWiSA)

Long-term gust speed (GS) measurements were used to develop a winter storm atlas of the 98 most severe winter storms in Germany in the period 1981–2018 (GeWiSa). The 25 m × 25 m storm-related GS fields were reconstructed in a two-step procedure: Firstly, the median gust speed ( G S ˜ ) of all winter storms was modeled by a least-squares boosting (LSBoost) approach. Orographic features and surface roughness were used as predictor variables. Secondly, the quotient of GS related to each winter storm to G S ˜ , which was defined as storm field factor (STF), was calculated and mapped by a thin plate spline interpolation (TPS). It was found that the mean study area-wide GS associated with the 2007 storm Kyrill is highest (29.7 m/s). In Southern Germany, the 1999 storm Lothar, with STF being up to 2.2, was the most extreme winter storm in terms of STF and GS. The results demonstrate that the variability of STF has a considerable impact on the simulated GS fields. Event-related model validation yielded a coefficient of determination (R2) of 0.786 for the test dataset. The developed GS fields can be used as input to storm damage models representing storm hazard. With the knowledge of the storm hazard, factors describing the vulnerability of storm exposed objects and structures can be better estimated, resulting in improved risk management.

Communicating the amount of windstorm induced forest damage by the maximum wind gust speed in Finland

Windstorms are natural disturbance agents in forests playing a role in natural forest regeneration. In Finland, the most severe individual windstorms have commonly damaged 2–4 million m3 of timber. In addition to financial losses caused to forest owners, windthrown trees have in many cases seriously disrupted the functionality of the national power grid. Communicating windstorm risks in duty forecasting is difficult. In this study, we aimed at developing windstorm impact estimates for forest damage in Finland to help the forecaster to improve communication of the risks of windstorms. We have compared the volume of forest damage caused by the most intense windstorms in Finland during the recent decade to the observed maximum inland wind gust speeds associated with the same windstorms. It was found out that the volume of forest damage follows approximately a power relation as a function of wind gust speed with a power of ∼10. This is a tentative estimate because of a short time series and small number of inspected windstorms. Moreover, also wind direction, location of the affected area and soil properties among other factors have an impact to the amount of damage as illustrated in our inspection. Despite the shortness of the time series, we believe that our results demonstrating the steep increase in the impacts of windstorms with an increasing windstorm intensity are valuable. However, more detailed investigations with longer time series are needed in order to more specifically communicate the windstorm risks and their impacts in boreal forests.