scholarly journals Polarimetric Radar Characteristics of Melting Hail. Part I: Theoretical Simulations Using Spectral Microphysical Modeling

2013 ◽  
Vol 52 (12) ◽  
pp. 2849-2870 ◽  
Author(s):  
Alexander V. Ryzhkov ◽  
Matthew R. Kumjian ◽  
Scott M. Ganson ◽  
Alexander P. Khain
Keyword(s):  
Particle Density ◽  
Lapse Rate ◽  
Size Analysis ◽  
Size Spectrum ◽  
Vertical Profiles ◽  
Polarimetric Radar ◽  
Temperature Lapse Rate ◽  
Freezing Level ◽  
Practical Algorithms ◽  
The Impact

AbstractSpectral (bin) microphysics models are used to simulate polarimetric radar variables in melting hail. Most computations are performed in a framework of a steady-state, one-dimensional column model. Vertical profiles of radar reflectivity factor Z, differential reflectivity ZDR, specific differential phase KDP, specific attenuation Ah, and specific differential attenuation ADP are modeled at S, C, and X bands for a variety of size distributions of ice particles aloft. The impact of temperature lapse rate, humidity, vertical air velocities, and ice particle density on the vertical profiles of the radar variables is also investigated. Polarimetric radar signatures of melting hail depend on the degree of melting or the height of the radar resolution volume with respect to the freezing level, which determines the relative fractions of partially and completely melted hail (i.e., rain). Simulated vertical profiles of radar variables are very sensitive to radar wavelength and the slope of the size distribution of hail aloft, which is correlated well with maximal hail size. Analysis of relative contributions of different parts of the hail/rain size spectrum to the radar variables allows explanations of a number of experimentally observed features such as large differences in Z of hail at the three radar wavelengths, unusually high values of ZDR at C band, and relative insensitivity of the measurements at C and X bands to the presence of large hail exceeding 2.5 cm in diameter. Modeling results are consistent with S- and C-band polarimetric radar observations and are utilized in Part II for devising practical algorithms for hail detection and determination of hail size as well as attenuation correction and rainfall estimation in the presence of hail.

scholarly journals MODELING THE IMPACT OF SURFACE CHARACTERISTICS ON THE NEAR SURFACE TEMPERATURE LAPSE RATE

2019 ◽  
Vol XLII-4/W18 ◽  
pp. 395-399 ◽  
Author(s):  
M. K. Firozjaei ◽  
S. Fathololuomi ◽  
S. K. Alavipanah ◽  
M. Kiavarz ◽  
A. Vaezi ◽  
...  
Keyword(s):  
Land Use ◽  
Surface Temperature ◽  
Feature Space ◽  
Surface Characteristics ◽  
Lapse Rate ◽  
Landsat 8 ◽  
Near Surface ◽  
Temperature Lapse Rate ◽  
Topographic Characteristics ◽  
The Impact

Abstract. Modeling of Near-Surface Temperature Lapse Rate (NSTLR) is very important in various environmental applications. The Land Surface Temperature (LST) is influenced by many properties and conditions including surface biophysical and topographic characteristics. Some researches have considered the LST - Digital Elevation Model (DEM) feature space to model NSTLR. However, the influence of detailed surface characteristics is rare. This study investigated the impact of surface characteristics on the LST-DEM feature space for NSTLR modeling. A set of remote sensing data including Landsat 8 images, MODIS products, and surface features including DEM and land use of the Balikhli-Chay on 01/07/2018, 18/08/2018 and 03/09/2018 were collected and used in this study. First, Split Window (SW) algorithm was used to estimate LST, and spectral indices were employed to model surface biophysical characteristics. Owing to the impact of surface biophysical and topographic characteristics on the LST-DEM feature space, the NSTLR was calculated for different classes of surface biophysical characteristics, land use, and solar local incident angle. The modeled NSTLR values based on the LST-DEM feature space on 01/07/2018, 18/08/2018 and 03/09/2018 were 8.5, 1.5 and 2.4 °C Km−1; respectively. The NSTLR in different classes of surface biophysical characteristics, land use type and topographical parameters were variable between 0.5 to 14 °C Km−1. This clearly showed the dependence of NSTLR on topographic and biophysical conditions. This provides a new way of calculating surface characteristic specific NSTLR.

scholarly journals The Impact of Raindrop Collisional Processes on the Polarimetric Radar Variables

2014 ◽  
Vol 71 (8) ◽  
pp. 3052-3067 ◽  
Author(s):  
Matthew R. Kumjian ◽  
Olivier P. Prat
Keyword(s):  
Electromagnetic Scattering ◽  
Vertical Profiles ◽  
Polarimetric Radar ◽  
Horizontal Polarization ◽  
One Dimensional ◽  
Microphysical Process ◽  
Warm Rain ◽  
Microphysical Processes ◽  
Differential Reflectivity ◽  
The Impact

Abstract The impact of the collisional warm-rain microphysical processes on the polarimetric radar variables is quantified using a coupled microphysics–electromagnetic scattering model. A one-dimensional bin-microphysical rain shaft model that resolves explicitly the evolution of the drop size distribution (DSD) under the influence of collisional coalescence and breakup, drop settling, and aerodynamic breakup is coupled with electromagnetic scattering calculations that simulate vertical profiles of the polarimetric radar variables: reflectivity factor at horizontal polarization ZH, differential reflectivity ZDR, and specific differential phase KDP. The polarimetric radar fingerprint of each individual microphysical process is quantified as a function of the shape of the initial DSD and for different values of nominal rainfall rate. Results indicate that individual microphysical processes (collisional processes, evaporation) display a distinctive signature and evolve within specific areas of ZH–ZDR and ZDR–KDP space. Furthermore, a comparison of the resulting simulated vertical profiles of the polarimetric variables with radar and disdrometer observations suggests that bin-microphysical parameterizations of drop breakup most frequently used are overly aggressive for the largest rainfall rates, resulting in very “tropical” DSDs heavily skewed toward smaller drops.

Flyash Adhesion in Simulated Coal-Fired Gas Turbine Environment

1989 ◽  
Vol 111 (4) ◽  
pp. 672-678 ◽  
Author(s):  
R. K. Ahluwalia ◽  
K. H. Im ◽  
R. A. Wenglarz
Keyword(s):  
Gas Turbine ◽  
Particle Density ◽  
Impact Angle ◽  
Size Spectrum ◽  
Pressure Surface ◽  
Analytical Scheme ◽  
Measured Weight ◽  
Weight Gain Data ◽  
The Impact ◽  
Sticking Coefficients

A rich-quench-lean subscale turbine combustor has been used to expose specimens to the products of combustion from several beneficiated coal-water fuels. An analytical scheme is formulated to extract sticking coefficients from the measured weight gain data, particle size spectrum, and particle density and composition. The inferred sticking coefficients, appropriate for impaction on the pressure surface, range between 0.0003 and 0.11 and are strong functions of the gas and surface temperatures but rather insensitive to the impact angle. The implications of these results on coal-fired gas turbine operation are discussed.

scholarly journals Impact of gravity waves on the motion and distribution of atmospheric ice particles

2018 ◽  
Vol 18 (14) ◽  
pp. 10799-10823 ◽  
Author(s):  
Aurélien Podglajen ◽  
Riwal Plougonven ◽  
Albert Hertzog ◽  
Eric Jensen
Keyword(s):  
Relative Humidity ◽  
Gravity Waves ◽  
Ice Crystals ◽  
Lapse Rate ◽  
Temperature Lapse Rate ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Ice Particles ◽  
The Pacific ◽  
The Impact

Abstract. Gravity waves are an ubiquitous feature of the atmosphere and influence clouds in multiple ways. Regarding cirrus clouds, many studies have emphasized the impact of wave-induced temperature fluctuations on the nucleation of ice crystals. This paper investigates the impact of the waves on the motion and distribution of ice particles, using the idealized 2-D framework of a monochromatic gravity wave. Contrary to previous studies, special attention is given to the impact of the wind field induced by the wave. Assuming no feedback of the ice on the water vapor content, theoretical and numerical analyses both show the existence of a wave-driven localization of ice crystals, where some ice particles remain confined in a specific phase of the wave. The precise location where the confinement occurs depends on the background relative humidity, but it is always characterized by a relative humidity near saturation and a positive vertical wind anomaly. Hence, the wave has an impact on the mean motion of the crystals and may reduce dehydration in cirrus by slowing down the sedimentation of the ice particles. The results also provide a new insight into the relation between relative humidity and ice crystals' presence. The wave-driven localization is consistent with temperature–cirrus relationships recently observed in the tropical tropopause layer (TTL) over the Pacific during the Airborne Tropical Tropopause EXperiment (ATTREX). It is argued that this effect may explain such observations. Finally, the impact of the described interaction on TTL cirrus dehydration efficiency is quantified using ATTREX observations of clouds and temperature lapse rate.

Interpreting mountain treelines in a changing world

2021 ◽  
Author(s):  
Surendra P. Singh ◽  
Ripu Daman Singh ◽  
Surabhi Gumber
Keyword(s):  
Climate Change ◽  
Water Relations ◽  
Distribution Patterns ◽  
Lapse Rate ◽  
Temperature Lapse Rate ◽  
Tree Phenology ◽  
Research Organizations ◽  
Spatial Dimensions ◽  
The Impact

Though the highest treelines of the northern hemisphere occur in the Himalaya, the terms treeline and timberline have until very recently been missing from the literature on this region. This book, largely based on research in the Indian Himalaya, attempts to fill the gap on Himalayan treelines. It covers ecology, tree water relations, temperature lapse rate, dendrochronology, tree phenology, distribution patterns, and spatial dimensions of climate warming over the decades. The project, led by the Central Himalayan Environment Association (CHEA) involved 6 research organizations, 11 investigators, and 20 research scholars. Treeline research is providing new and valuable insights into how biota respond to climate change, the relationship between tree-ring growth and climate change in various seasons, the role of growth in relation to stress, seasonal variation in temperature lapse rate and the impact of elevation dependent warming, tree water relations and water conduits in trees, effects of early snow melt, endemism, and future changes.

scholarly journals Impact of gravity waves on the motion and distribution of atmospheric ice particles

2017 ◽  
Author(s):  
Aurélien Podglajen ◽  
Riwal Plougonven ◽  
Albert Hertzog ◽  
Eric Jensen
Keyword(s):  
Relative Humidity ◽  
Gravity Waves ◽  
Ice Crystals ◽  
Lapse Rate ◽  
Temperature Lapse Rate ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Ice Particles ◽  
The Pacific ◽  
The Impact

Abstract. Gravity waves are an ubiquitous feature of the atmosphere and influence clouds in multiple ways. Regarding cirrus clouds, many studies have emphasized the impact of wave-induced temperature fluctuations on the nucleation of ice crystals. This paper investigates the impact of the waves on the motion and distribution of ice particles, using the idealized 2-D framework of a monochromatic gravity wave. Contrary to previous studies, a special attention is given to the impact of the wind field induced by the wave. Assuming no feedback of the ice on the water vapor content, theoretical and numerical analyses both show the existence of a wave-driven localization of ice crystals, where some ice particles remain confined in a specific phase of the wave. The precise location where the confinement occurs depends on the background relative humidity, but it is always characterized by a relative humidity near saturation and a positive vertical wind anomaly. Hence, the wave has an impact on the mean motion of the crystals and may reduce dehydration in cirrus by slowing down the sedimentation of the ice particles. The results also provide a new insight into the relation between relative humidity and ice crystals presence. The wave-driven localization is consistent with temperature-cirrus relationships recently observed in the tropical tropopause layer (TTL) over the Pacific during the Airborne Tropical Tropopause EXperiment (ATTREX). It is argued that this effect may explain such observations. Finally, the impact of the described interaction on TTL cirrus dehydration efficiency is quantified using ATTREX observations of clouds and temperature lapse rate.

Visual Evidence of Constrained Area of a Cloudburst, 12 June 2018, Tirisha Village, Nubra Valley, Ladakh, India

2020 ◽  
Vol 6 (2) ◽  
pp. 47-57
Author(s):  
Renoj J. Thayyen ◽  
Mritunjay Kumar Singh ◽  
A.P. Dimri
Keyword(s):  
Satellite Data ◽  
Flash Flood ◽  
Satellite Image ◽  
Lapse Rate ◽  
Mountain Ridge ◽  
Temperature Lapse Rate ◽  
Visual Evidence ◽  
Impact Area ◽  
The Impact ◽  
First Time

On 12 June 2018, the Tirisha village in Nubra valley, Ladakh experienced a flash flood from a cloudburst that occurred over the mountain ridge. This event was captured in a Sentinel 2B satellite image at the time of its occurrence. The image also provided unique visual evidence of the constrained area of a cloudburst for the first time. Field survey of impact area at the Tirisha village was carried out on 13 June 2018. It was followed by assessment of the impact at the place of occurrence and further downstream using satellite data taken on, before and subsequent days. Satellite data show small area where cloudburst impact (< 1km2) from a cumulonimbus (Cb) cell of ~2.97 km2 of cloud top area. Rest of the flood catchment remained cloud-free during the event and floodwater in the stream is clearly visible in the imagery. The flash flood entered the Tirisha village situated at the Nubra valley foothills, which destroyed a stretch of 100 m road. Previous studies have suggested inherent atmospheric instability over the arid Ladakh region with an extremely high-temperature lapse rate of >9.8 K/km during 40-70 days during summer months. The extremely constrained nature of this event highlights the challenges involved in monitoring, forecasting and managing such events in the Himalayan region.

A Macroeconomic Analysis of Agricultural Sector in Nigeria

2019 ◽  
Vol 5 (1) ◽  
pp. 18-25
Author(s):  
Isah Funtua Abubakar ◽  
Umar Bambale Ibrahim
Keyword(s):  
Value Chain ◽  
Crop Production ◽  
Agricultural Sector ◽  
Time Series Data ◽  
Tourism Industry ◽  
Series Data ◽  
Size Analysis ◽  
The Real ◽  
Real Gdp ◽  
The Impact

This paper attempts to study the Nigerian agriculture industry as a panacea to growth as well as an anchor to the diversification agenda of the present government. To do this, the time series data of the four agriculture subsectors of crop production, livestock, forestry and fishery were analysed as stimulus to the Real GDP from 1981-2016 in order to explicate the individual contributions of the subsectors to the RGDP in order to guide the policy thrust on diversification. Using the Johansen approach to cointegration, all the variables were found to be cointegrated. With the exception of the forestry subsector, all the three subsectors were seen to have impacted on the real GDP at varying degrees during the time under review. The crop production subsector has the highest impact, however, taking size-by-size analysis, the livestock subsector could be of much importance due to its ability to retain its value chain and high investment returns particularly in poultry. Therefore, it is recommended that, the government should intensify efforts to retain the value chain in the crop production subsector, in order to harness its potentials optimally through the encouragement of the establishment of agriculture cottage industries. Secondly, the livestock subsector is found to be the most rapidly growing and commercialized subsector. Therefore, it should be the prime subsector to hinge the diversification agenda naturally. Lastly, the tourism industry which is a source through which the impact of the subsector is channeled to the GDP should be developed, in order to improve the impact of such channel to GDP with the sole objective to resuscitate the forestry subsector.

scholarly journals Observations of Winter Ablation on Glaciers in the Mount Everest Region in 2020–2021

2021 ◽  
Vol 13 (14) ◽  
pp. 2692
Author(s):  
Mauri Pelto ◽  
Prajjwal Panday ◽  
Tom Matthews ◽  
Jon Maurer ◽  
L. Baker Perry
Keyword(s):  
Remote Sensing Data ◽  
Time Data ◽  
Mount Everest ◽  
Monsoon Period ◽  
National Geographic ◽  
Freezing Level ◽  
Post Monsoon ◽  
Base Camp ◽  
Dry Conditions ◽  
The Impact

Recent observations of rising snow lines and reduced snow-covered areas on glaciers during the October 2020–January 2021 period in the Nepal–China region of Mount Everest in Landsat and Sentinel imagery highlight observations that significant ablation has occurred in recent years on many Himalayan glaciers in the post-monsoon and early winter periods. For the first time, we now have weather stations providing real-time data in the Mount Everest region that may sufficiently transect the post-monsoon snow line elevation region. These sensors have been placed by the Rolex National Geographic Perpetual Planet expedition. Combining in situ weather records and remote sensing data provides a unique opportunity to examine the impact of the warm and dry conditions during the 2020 post-monsoon period through to the 2020/2021 winter on glaciers in the Mount Everest region. The ablation season extended through January 2021. Winter (DJF) ERA5 reanalysis temperature reconstructions for Everest Base Camp (5315 m) for the 1950–February 2021 period indicate that six days in the January 10–15 period in 2021 fell in the top 1% of all winter days since 1950, with January 13, January 14, and January 12, being the first, second, and third warmest winter days in the 72-year period. This has also led to the highest freezing levels in winter for the 1950–2021 period, with the January 12–14 period being the only period in winter with a freezing level above 6000 m.

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