Diurnal variations of outgoing long wave radiation (OLR) vis a vis 4 January, 2016 Manipur earthquake (Mw: 6.7): An earthquake precursor?

Daily and diurnal variations of OLR from INSAT 3D and Kalpana satellites have been studied during 25 December, 2015 to 5 January, 2016 over the epicentral region of the Manipur earthquake of 4 January, 2016 (Mw 6.7) and other regions within the view of these satellites. The surface temperatures recorded at Imphal around 30 km from epicentre of this earthquake were also examined. It is found that OLR remained low prior to the occurrence of Manipur earthquake while much larger rise occurred over several other regions where no significant seismic activity was reported. The results corroborate inferences reported in earlier studies that OLR or temperature changes are related to meteorological causes and its sole identification as earthquake precursor may be misleading due to poor constraints.

Mitigating urban heat island effect through integrated climate-sensitive planning framework: a study based in Singapore

<p><strong>Background</strong></p><p>Urban heat island (UHI) is known as one of the severe environmental problems, and thus, research on UHI mitigation from the perspective of urban morphology is indispensable, especially in tropical regions like Singapore.</p><p><strong>Objectives</strong></p><p>While studies were carried out to evaluate and relieve UHI effect in urban areas, research that conducted through integrated assessment of urban aerodynamic and long wave radiation is limited. This research aims to provide an integrated climate-sensitive planning framework to UHI mitigation by understanding urban morphology.</p><p><strong>Methods</strong></p><p>A district-scale case study in Paya Lebar Air Base (PLAB) was conducted to illustrate how the urban morphological study contributes to the initial planning by an integrated analysis of climate information. Two urban morphological indices, frontal area density (FAD) and sky view factor (SVF), were calculated to depict aerodynamic and long wave radiation, i.e., pedestrian-level wind speed and air temperature, respectively.</p><p><strong>Results</strong></p><p>The SVF modelling results indicate that the UHI intensity at surrounding areas could be 2℃ to 3℃. With future development, there is a potential risk to create a spreading and more intensive UHI. Aiming at this problem, the FAD map indicates the importance of linking open spaces to create air paths, while the ΔT map implies the necessity of separating building clusters with intensive UHI. Integrated planning strategies are then developed based on the balance between link and separation, focusing on site layout and building geometry. For site layout, open spaces, e.g., major roads, building setbacks, low-rise built areas, and green corridor, should be linked to form the potential breezeways. At the same time, buffer zones like secondary forest should be arranged between site and surrounding areas to prevent new and existing UHI clusters from merging together. As for the building geometry, as the important design parameters, building height, footprint area, and building height to width ratio (H/W) should be carefully decided. Accordingly, a multi-step workflow is developed as an integrated climate-sensitive planning framework.</p><p><strong>Conclusions</strong></p><p>Urban morphology makes an important contribution to UHI effect. Integrated UHI mitigations can be developed by balancing the strategies for spatial link and separation in urban planning and design, based on climate information, e.g., aerodynamics and heat. The integrated climate-sensitive planning framework is generally applicable to tropical regions with cooling needs, as the key is to minimize temperature rise due to long wave radiation while introduce cool air to the site.</p>

The surface energy balance of the Sygyktinsky glacier (Kodar ridge, Eastern Siberia) during the ablation periods of 2019 and 2020 and its sensitivity to meteorological conditions

<p>The surface energy balance (SEB) of a glacier during ablation period describes the physical process of melting and its relationship to climatic fluctuations. Unfortunately, there is little experimental data on physically substantiated processes of melting of continental Siberian glaciers. In this study, we modeled the components of the SEB of a small low altitude continental glacier located in inland Asia (Eastern Siberia, Kodar ridge, 56° 51 'N, 117° 25' E, 2561 m above sea level ). The Kodar glaciers (about 40 small glaciers) have been shrinking since the end of the Little Ice Age and have experienced an accelerated area decline in the 1990s. To study the SEB components we installed two automatic weather stations (AWS) directly on the glacier and its terminal moraine during the two ablation seasons (July–August of 2019 and 2020). Such parameters as meteorological characteristics (air temperature, relative humidity, precipitation, wind speed and direction, atmospheric pressure, temperature of the upper glacier layer) as well as radiation fluxes (short-wave and long-wave radiation) were measured with a 30-minute resolution. Turbulent fluxes were estimated using the bulk aerodynamic approach. Daily ice melting was directly measured using ablation stakes and a thermometric method. As a result, we found that the net radiation was the main source of surface snow/ice melting (84–93% of total energy for melt), followed by sensible heat (5–9%) and latent heat of condensation (3–7%). The simulated ablation is in good agreement with the measured one. Albedo strongly affects the net radiation and demonstrates two clearly distinguished regimes due to the presence or absence of snow cover on the glacier. During the first half of the ablation season (July) albedo decreases almost linearly, and during the second (August) it has low background values with pronounced spikes due to short-term summer snowfalls. The net radiation and melting regime are strongly influenced by summer cloudiness, which reaches 70–80% ​​as a result of the intensification of cyclonic processes over the Kodar region. Heat losses due to long-wave radiation were recorded only in summer of 2019 (–15 W m<sup>–2</sup>), while in 2020 the net long-wave radiation was slightly above zero (3 W m<sup>–2</sup>). This is explained by the more significant (10% more) cloud fraction in 2020 over the study area. Thus, almost all heat supplied to the glacial surface spends on melting snow and ice. The influence of solar radiation factors on ice melting indicates the need to take into account long-term trends in the processes of atmospheric circulation (fluctuations of cyclones and anticyclones) when explaining the acceleration in ice area reduction of the Kodar glaciers in 1990s. This study was supported by the Russian Foundation for Basic Research (project No. 19-05-00668).</p>

The surface energy balance in a cold and arid permafrost environment, Ladakh, Himalayas, India

Recent studies have shown the cold and arid trans-Himalayan region comprises significant areas underlain by permafrost. While the information on the permafrost characteristics of this region started emerging, the governing energy regime is of particular interest. This paper presents the results of a surface energy balance (SEB) study carried out in the upper Ganglass catchment in the Ladakh region of India which feeds directly into the Indus River. The point-scale SEB is estimated using the 1D mode of the GEOtop model for the period of 1 September 2015 to 31 August 2017 at 4727 m a.s.l. elevation. The model is evaluated using field-monitored snow depth variations (accumulation and melting), outgoing long-wave radiation and near-surface ground temperatures and showed good agreement with the respective simulated values. For the study period, the SEB characteristics of the study site show that the net radiation (29.7 W m−2) was the major component, followed by sensible heat flux (−15.6 W m−2), latent heat flux (−11.2 W m−2) and ground heat flux (−0.5 W m−2). During both years, the latent heat flux was highest in summer and lowest in winter, whereas the sensible heat flux was highest in post-winter and gradually decreased towards the pre-winter season. During the study period, snow cover builds up starting around the last week of December, facilitating ground cooling during almost 3 months (October to December), with sub-zero temperatures down to −20 ∘C providing a favourable environment for permafrost. It is observed that the Ladakh region has a very low relative humidity in the range of 43 % compared to e.g. ∼70 % in the European Alps, resulting in lower incoming long-wave radiation and strongly negative net long-wave radiation averaging ∼-90 W m−2 compared to −40 W m−2 in the European Alps. Hence, land surfaces at high elevation in cold and arid regions could be overall colder than the locations with higher relative humidity, such as the European Alps. Further, it is found that high incoming short-wave radiation during summer months in the region may be facilitating enhanced cooling of wet valley bottom surfaces as a result of stronger evaporation.

Modelling parametrization to estimate atmospheric long wave radiation in the Northern Mato Grosso, Brazil

The measures of Atmospheric Long Wave radiation are onerous, which brings the necessity to use alternative methods. Thus, the main aim of this paper was to test and parameterize some models that exist in the literature to estimate atmospheric long wave. The data were collected at Fazenda São Nicolau (2002 - 2003), located in Northwestern of Mato Grosso State. Data were processed hourly, monthly, and seasonal (dry and wet) besides clear and partly cloudy days on the average. The models of Swinbank, Idso Jackson, Idso, Prata and Duarte. were applied. The performance of the models was based on the mean error, square root of mean square error, absolute mean error, Pearson's coefficient and Willmott's coefficient. All models had presented high errors and low Peason’s and Willmott coefficients. After parameterizing, all models reduced their errors and increased Pearson and Willmott’s coefficient. The models of Idso and Swinbank had presented better and worse performance, respectively. It was not observed an increment on the performance of the model when classified according to cloudiness and seasonality. The Idso’s model had presented the lowest errors among the models. The model that had presented worst performance for any tested situation was Swinbank.

The influence of radiative forcing on permafrost temperatures in Arctic rock walls

<p>Climate change has a strong impact on periglacial regions and intensifies the degradation of mountain permafrost. This can result in instabilities of steep rock walls as rock- and ice-mechanical properties are modified. Besides altitude and the related air temperature, latitude is a crucial factor, as solar radiation has a strong impact on the energy transfer processes from the atmosphere to the ground. It can differ significantly in intensity and time over latitudinal positions and exposures of frozen rock slopes.</p><p>In this project, we suggest improving the parametrization of short-wave and long-wave radiation in thermal models for permafrost degradation. To achieve this, we will analyze temperature data of surface temperature loggers from Southern Norway to Svalbard. In total, 37 loggers were installed between 2010 and 2017. The field sites display enormous latitudinal gradients as well as topographic settings. Furthermore, they provide hourly data, allowing us to set up short-stepped time series for examination of solar radiation angles at varying latitudes.</p><p>The data is used to set up a transient heat-flow model (CryoGrid) to simulate the local thermal regime. The model takes into account varying input of short-wave radiation due to aspect, slope angle and time as well as long-wave radiation under different sky-view factors. Finally, the influence of solar radiation on permafrost degradation in steep rock walls is investigated.</p>

Energy exchange between surface and atmosphere on the Severnaya Zemlya archipelago in 2013 – 2019 years

<p>Based on the data of meteorological observations, executed in 2013-2019 at Research Station “Ice base Cape Baranova” (RS) and original algorithm, taken into account accuracy of measurements and footprints, the components of surface heat budget are calculated. It is shown that in winter due to radiation cooling turbulent sensible heat flux (H) directs to underlying surface. In summer H due to radiation heating of surface with low albedo directs to atmosphere and reaches 25% of the incoming short-wave radiation. The turbulent latent heat flux (LE) in winter directs to atmosphere. Its value is not more than 10% of H. During summer LE has no predominant direction. </p><p>Comprehensive monitoring carried out at RS since 2013 allowed to examine the role of large-scale processes in the polar atmosphere and hydrosphere on the formation of local climate in the region. In 2016, 2018 and 2019 sea ice cover of the Barents and Kara Seas in October, the month of active freezing of active soil layer, occupied the minimal area starting 1978 year (http://wdc.aari.ru/datasets/d0042/). This circumstance along with peculiarities of circulation processes in the atmosphere had led to anomalous of temperature and humidity regimes of lower troposphere. These years monthly mean air temperature up to 700 hPa was about -4 °C compared to -7 - -11 °C in 2013 - 2015 and 2017. In 2016 the lower troposphere was warmer by 2 - 3 °C  and specific humidity in atmospheric boundary layer was 30–60% higher its values in 2013–2015 and 2017. Even in 2018, when the area of open water adjacent to the Severnaya Zemlya archipelago was significantly larger than in 2016, specific humidity at altitudes up to 3 km was 4-12 percents less.</p><p>In 2016 monthly mean wind speed, mainly of southwestern direction, reached maximum value, more than 7 m/s. It led to weakening of atmospheric surface layer stratification (z/L <0.2). The air specific humidity  significantly increased also, up to 3.0 and 2.7 g /kg at 2 meters and at z<sub>0</sub> . Long-wave radiation fluxes increased by more than 15 – 20 W/m<sup>2</sup>. Same time due to increase of underlying surface temperature, its long-wave radiation cooling, which was not compensated by the increase of incoming long-wave radiation increased up to -27 W/m<sup>2</sup>. H, directed to the underlying surface, increased to 10 W/m<sup>2  </sup>and LE, directed to atmosphere, increased almost 2 times, up to 12 W/m<sup>2</sup>. As a result of multidirectional changes of heat fluxes, defining surface heat balance, its value in October 2016 (-31.6 W/m<sup>2</sup>) was comparable to calculated for other years.</p><p>The most probable explanation of the revealed features of atmospheric boundary and surface layers in October 2016 are the absence of sea ice cover in the waters, adjacent to the archipelago, prevented cooling of atmosphere, and strong zonal component of the wind velocity, caused the transfer of warm and moist air masses of Atlantic origin into the study area.</p><p>The work had been done under financial support of the Ministry of Science and Higher Education of the Russian Federation (project no. RFMEFI61619X0108).</p>