Temperature Depth Research Articles

CTD Sensors for Ocean Investigation Including State of Art and Commercially Available.

Over 70% of the earth's surface is covered by oceans; globally, oceans provides a huge source of wealth to humans. In the literature, several sensors have been developed to investigate oceans. Electrical conductivity temperature depth (CTD) sensors were used frequently and extensively. Long-term accurate CTD data is important for the study and utilization of oceans, e.g., for weather forecasting, ecological evolution, fishery, and shipping. Several kinds of CTD sensors based on electrics, optical, acoustic wave and radio waves have been developed. CTD sensors are often utilized by measuring electrical signals. The latest progress of CTD sensors will be presented in order of performance. The principles, structure, materials and properties of many CTD sensors were discussed in detail. The commercially available CTD sensors were involved and their respective performances were compared. Some possible development directions of CTD sensors for ocean investigation are proposed.

Improving Accuracy of Horizontal Flow Field Using Acoustic Tomography With Real-Time Station Position Correction

High-precision and spatiotemporal flow field measurement in small-scale waters has a decisive impact on navigation and water resource management. Multitransmission rays and position drift, as two main difficulties in improving the accuracy of small-scale flow field, need to be solved urgently. In this article, four coastal acoustic tomography (CAT) systems are arranged in Qingyang Lake, Hunan, China, on March 1, 2022, for a short-term observation. As the GPS error and shipping caused station drift contaminate the reconstructed flow field, a real-time station position correction method, based on travel time and temperature, depth (TD) sensors, is applied in our inversion. The inversion range average current (RAC) is in agreement with forward calculation, which proves the reliability of the reconstructed horizontal flow field. Besides, comparisons of net flow and acoustic Doppler current profiler (ADCP) velocity are performed to validate the improvement of the real-time station position correction algorithm. The errors of the corrected net flow are less than 3.818 m 2/s, with a minimum of 0.0042 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{2}$ </tex-math></inline-formula> /s. The root-mean-square error (RMSE) between the CAT inversion results and the ADCP velocity is 0.123 m/s after correction, relatively reduced 5.95% than before correction. The smaller the RMSE, the higher the inversion accuracy, so the CAT method with real-time station position correction is feasible for high-precision horizontal flow field reconstruction.

Spatio-temporal dynamics of dissolved oxygen and its influencing factors in Lake Xiannv Jiangxi, China

为探究深水湖库溶解氧的时空分布规律及其主控因素，本文以南方亚热带大型深水湖库——江西省仙女湖为研究对象，基于2008—2021年仙女湖4个国控站点溶解氧的历史数据分析其年际变化的规律及原因；另于2016年水污染事件发生前（2014年5月-2015年4月）及水污染事件结束后（2018年1月-2018年12月）对仙女湖进行加密逐月监测，采用结构方程模型（SEM）分析仙女湖溶解氧的主要驱动因素。研究结果表明，2008—2021年仙女湖水体溶解氧浓度先下降后上升，变化范围为5.1~18.7 mg/L，季节均值为春季>冬季>秋季>夏季。水污染事件发生前高溶解氧区域多出现在舞龙湖湖心区及湖出口位置，水温、叶绿素a浓度和浊度是溶解氧浓度变化的主要驱动因素；水污染事件结束后高溶解氧区域多出现在钤阳湖及舞龙湖枝杈状湖湾位置，叶绿素a浓度及营养盐浓度成为溶解氧浓度变化的主要驱动因素；而pH与溶解氧主要是协同变化的关系。根据对仙女湖最深点（江口）的垂向监测结果，溶解氧的垂向差异为夏季>秋季>春季>冬季，夏、秋季在5 m以下出现低溶解氧（DO<5 mg/L）区域，且夏季观察到明显的温跃层及温跃层内溶解氧的极小值现象。总体来说，水污染事件使得仙女湖水体营养平衡被打破，营养盐浓度大幅上升导致的浮游植物数量增多是仙女湖水体表层溶解氧浓度升高的主要原因，而深水溶解氧浓度变化则与水温、水深密切相关。;To systematically explore the spatial-temporal distribution and main controlling factors of dissolved oxygen (DO) in deep lakes, we take Lake Xiannv, a large subtropical reservoir in south China, as the research object. By collecting the historical data of DO at four state-controlled points in Lake Xiannv from 2008 to 2021 to analyze its interannual changes. We also conducted intensive monthly monitoring of Lake Xiannv from May 2014 to April 2015 and from January 2018 to December 2018, which were before and after the water pollution accident in 2016. The factors influencing DO in Lake Xiannv were quantitatively analyzed by the structural equation model (SEM). Results showed that from 2008 to 2021, the DO concentration of Lake Xiannv first decreased and then increased, with a range of 5.1-18.7 mg/L, and the seasonal means were spring>winter>autumn>summer. Before the water pollution accident, the DO concentration in the central area and the outlet of Lake Wulong was higher and water temperature, chlorophyll-a and turbidity were the main driving factors for the change of DO. After the accident, the DO concentration in Lake Qianyang and the bays of Lake Wulong was higher and chlorophyll-a and water nutrition were the main driving factors for the change of DO. There are common changes between pH and DO. The vertical monitoring results of the deepest point (Jiangkou) showed that the vertical changes of water temperature and DO in Lake Xiannv were summer>autumn>spring>winter. We found that there were low DO (DO<5 mg/L) zones below 5 m of the lake in summer and autumn, thermocline and metalimnetic oxygen minimum (MOM) were observed in summer. In general, the water pollution accident broke the nutrient balance of Lake Xiannv, and the large increase in nutrient concentration led to an increase of phytoplankton, which was the main reason for the increase in DO concentration on the surface of Lake Xiannv, and the changing of deep-water DO concentration is closely related to water temperature and water depth.

Effect of selected environmental factors on the seed germination of the invasive species Polygala myrtifolia (Polygalaceae) in Australia

Context Polygala myrtifolia L. has become a significant environmental weed in Australia, where it has invaded coastal ecosystems in temperate regions and there is a high risk of extensive further spread. Knowledge of seed-germination behaviour is essential to understand the potential future impact of this species. Aims We investigated the effects of selected environmental factors and dormancy on P. myrtifolia seed germination and emergence to improve management strategies. Methods Seeds were exposed to light, temperature, pH, salinity, osmotic potential and burial depth treatments to assess germination responses, dormancy and viability. Key results Non-dormant seeds readily germinated to high percentages (93.0–95.0%) under specific day–night temperatures of 25°C–15°C regardless of light conditions and across all soil pH (75.0–100.0%). Salinities were tolerated up to 100 mM NaCl (70.0% germination) before sharply declining. Germination reduced from 98.3% to 40.0% at osmotic potentials of −0.4 MPa and −0.6 MPa respectively. Emergence was greatest on the soil surface (48.33%) and absent from depths of 8 cm. Conclusions Germination was high during autumn, winter and spring conditions and across soils of any pH. The species is unlikely to invade areas of high salinity; however, it is moderately tolerant of low soil moisture during germination. Implications There is high risk of P. myrtifolia further invading sensitive ecosystems because of its high germination success. Preventing seed dispersal and ensuring seedlings are controlled on emergence are critical to reducing its impact. We recommend that the cultivation and sale of this species should be prohibited across Australia to prevent further spread.

GNOMES II: Analysis of the Galactic diffuse molecular ISM in all four ground state hydroxyl transitions using Amoeba

Abstract We present observations of the four $^2 \Pi _{3/2}\,J=3/2$ ground-rotational state transitions of the hydroxyl molecule (OH) along 107 lines of sight both in and out of the Galactic plane: 92 sets of observations from the Arecibo telescope and 15 sets of observations from the Australia Telescope Compact Array (ATCA). Our Arecibo observations included off-source pointings, allowing us to measure excitation temperature ( $T_{\rm ex}$ ) and optical depth, while our ATCA observations give optical depth only. We perform Gaussian decomposition using the Automated Molecular Excitation Bayesian line-fitting Algorithm ‘Amoeba’ (Petzler, Dawson, &amp; Wardle 2021, ApJ, 923, 261) fitting all four transitions simultaneously with shared centroid velocity and width. We identify 109 features across 38 sightlines (including 58 detections along 27 sightlines with excitation temperature measurements). While the main lines at 1665 and 1667 MHz tend to have similar excitation temperatures (median $|\Delta T_{\rm ex}({\rm main})|=0.6\,$ K, 84% show $|\Delta T_{\rm ex}({\rm main})|&lt;2\,$ K), large differences in the 1612 and 1720 MHz satellite line excitation temperatures show that the gas is generally not in LTE. For a selection of sightlines, we compare our OH features to associated (on-sky and in velocity) Hi cold gas components (CNM) identified by Nguyen et al. (2019, ApJ, 880, 141) and find no strong correlations. We speculate that this may indicate an effective decoupling of the molecular gas from the CNM once it accumulates.

Fast and Expandable ANN-Based Compact Model and Parameter Extraction for Emerging Transistors

In this paper, we present a fast and expandable artificial neural network (ANN)-based compact model and parameter extraction flow to replace the existing complicated compact model implementation and model parameter extraction (MPE) method. In addition to nanosheet FETs (NSFETs), our published ANN-based compact modeling framework is easily extended to negative capacitance NSFETs (NC-NSFETs), which are attracting attention as next-generation devices. Each device is designed using a technology computer-aided design (TCAD) simulator. Using device structure parameters, temperature, and channel doping depth as input variables, we construct a dataset of electrical properties used for machine learning (ML)-based modeling. The accuracy of predicting device electrical characteristics with the proposed ANN-based compact model is less than a 1% error compared to TCAD, and simulation results of digital and analog circuits using the proposed compact model show less than a 3% error. This allows the ANN-based modeling framework to achieve accurate DC, AC, and transient simulations without restrictions on device technology. In particular, temperature and process variables such as channel doping depth, which are not defined in the compact model parameters, are easily added to the previously presented five key parameters. Instead of conventional complex compact modeling and MPE work, we propose a method to create fast, accurate, flexible, and expandable ML-based Verilog-A SPICE models with design technology co-optimization (DTCO) capabilities.

Parametric Subharmonic Instability of Diurnal Internal Tides in the Abyssal South China Sea

Abstract Internal waves close to the seafloor of abyssal oceans are the key energy suppliers driving near-bottom mixing and the upwelling branches of meridional overturning circulation, but their spatiotemporal variability and intrinsic mechanisms remain largely unclear. In this study, measurements from 10 long-term moorings were used to investigate the internal wave activities in the abyssal South China Sea, which is an important upwelling zone. Strong near-inertial internal waves (NIWs) with current velocity pulses exceeding 5 cm s−1 were observed to dominate the near-bottom internal wave field at approximately 14°N. These abyssal NIWs were phase-coupled with diurnal internal tides (D1), and both displayed common seasonal variations that were larger in winter and summer, providing evidence of diurnal parametric subharmonic instability (PSI) near its critical latitudes (CLs). Emitted from the bottom, near-inertial kinetic energy rapidly decreased by one order of magnitude from depths of ∼120 to ∼620 m above the bottom. Near rough topographies, the abyssal PSI was shifted poleward to approximately 14.8°N by negative relative vorticities of passing anticyclonic eddies or topographic Rossby waves. Compared with flat topography, PSI near rough topography was significantly promoted by topographic-localized strong D1 with high-mode structures, creating abyssal NIW bursts. Bottom-reaching shipboard conductivity–temperature–depth profiles revealed that the bottom mixed layers became much thicker when approaching CLs, suggesting that abyssal PSI potentially accelerates the ventilation and upwelling of bottom water. The observational results presented here illustrate notable spatiotemporal variations in abyssal NIWs regulated by PSI and call for consideration of PSI to better understand near-bottom mixing and upwelling.

Temperature and Secchi Disk Depth Increase More Rapidly in the Subpolar Bering/Okhotsk Seas Than in the Subtropical South China Sea

Like other high-latitude seas, the subpolar Bering and Okhotsk Seas in the northernmost Pacific Ocean changed rapidly from 1998 to 2018. The sea surface temperature (SST) increased by 0.62 and 0.41 °C/decade, respectively, much higher than the global rate of 0.108 °C/decade from 2000 until 2015. Despite this rapid warming, the chlorophyll content did not change significantly in the Bering Sea but increased by 0.047 μg/L/decade in the Okhotsk Sea. The Secchi disk depth (SDD) increased by 0.43 and 0.46 m/decade, respectively. Similar to other warm bodies of water, the SST of the subtropical/tropical South China Sea (SCS) also began rising, by 0.089 °C/decade, albeit more slowly than the global average. The chlorophyll content increased at 0.15 μg/L/decade from 1998 to 2006 but decreased by 0.11 μg/L/decade between 2007 and 2018. The SDD increased by 0.29 m/decade between 1998 and 2018. Although the SDD increased in all three seas, the chlorophyll concentration was maximum around 2006–2009, reflecting different phytoplankton responses to seawater warming.

Probing plasma physics with spectral index maps of accreting black holes on event horizon scales

ABSTRACT The Event Horizon Telescope (EHT) collaboration has produced the first resolved images of the supermassive black holes at the centre of our galaxy and at the centre of the elliptical galaxy M87. As both technology and analysis pipelines improve, it will soon become possible to produce spectral index maps of black hole accretion flows on event horizon scales. In this work, we predict spectral index maps of both M87* and Sgr A* by applying the general relativistic radiative transfer (GRRT) code ipole to a suite of general relativistic magnetohydrodynamic (GRMHD) simulations. We analytically show that the spectral index increases with increasing magnetic field strength, electron temperature, and optical depth. Consequently, spectral index maps grow more negative with increasing radius in almost all models, since all of these quantities tend to be maximized near the event horizon. Additionally, photon ring geodesics exhibit more positive spectral indices, since they sample the innermost regions of the accretion flow with the most extreme plasma conditions. Spectral index maps are sensitive to highly uncertain plasma heating prescriptions (the electron temperature and distribution function). However, if our understanding of these aspects of plasma physics can be tightened, even the spatially unresolved spectral index around 230 GHz can be used to discriminate between models. In particular, Standard and Normal Evolution (SANE) flows tend to exhibit more negative spectral indices than Magnetically Arrested Disc (MAD) flows due to differences in the characteristic magnetic field strength and temperature of emitting plasma.

Variation of upper-layer flow structures and water masses observed around the Noto Peninsula and Sado Island, Japan

After classifying various water masses around the Noto Peninsula and Sado Island, Japan and identifying their seasonal variation, we investigated flow fields in the area. Distributions of flow structures and water properties were analyzed based on intensive observations using a conductivity–temperature–depth profiler during 2002–2020. Tide gauge and satellite altimetry data were also analyzed to elucidate the temporal and the more widespread horizontal variation of the sea surface geostrophic flow field. Interannual change of the northeastward baroclinic jet formed offshore of the Noto Peninsula in fall was found. Furthermore, anticyclonic eddy formation around Toyama Bay which is part of the current path transition of the coastal branch of the Tsushima Warm Current was found to result from effects of bathymetric change behind the Noto Peninsula. At that time, the sea-surface current speed of the coastal branch was also high. We propose new methods for predicting current path transition events two weeks in advance.

Multi-layer flow field mapping in a small-scale shallow water reservoir by coastal acoustic tomography

Long-term, high-precision and spatiotemporal observation of current structure in small-scale waters is important for underwater research and water resources management. In this paper, a reciprocal sound transmission experiment was conducted using three Coastal Acoustic tomography (CAT) systems within 300 m spacing in Huangcai reservoir, Hunan, China from 14 to 16, Sep 2020. The multi-arrival reciprocal paths between each pair of stations were identified with the help of ray simulation. 3-D CAT data which penetrated the full depth of water were obtained. The flow field along vertical slice were mapped and showed consistency with Acoustic Doppler Current Profiler (ADCP) and Temperature Depth (TD) data. A standard deviation of 0.73 m/s at the bottom layer were observed, indicating strong bottom flows in the reservoir. Furthermore, to visualize the strong bottom flow, the horizontal flow fields in the bottom layer were mapped by 3-D inversion technique. The feasibility of the technique was validated by three measures: 1) comparison between range average current and horizontal flow field; 2) Uncertainty analysis; 3) Check net volume transport. This work proves the CAT combined with 3-D inversion technique has the potentials to provide real-time 3-D current data for water researches.

Genesis Mechanisms of Geothermal Resources in Mangkang Geothermal Field, Tibet, China: Evidence from Hydrochemical Characteristics of Geothermal Water

The Mangkang geothermal field, distributed in the Mediterranean–Himalayas geothermal belt, hosts abundant hot springs whose geneses remain unclear. To determine the hydrochemical characteristics, reservoir temperature, circulation and recharge depths, and water–rock interactions of the geothermal water in the geothermal field, this study analyzed hydrochemical compositions and isotopes (2H, 3H, and 18O), conducted a PHREEQC simulation, and established a conceptual model to illustrate the genesis of geothermal resources in the Mangkang field. Based on the study of hot springs in Meipu, Qvzika, and Zulongpu villages and Rumei town, the following results are reported: The orifice temperatures of these hot springs vary between 18 °C and 67.5 °C. The hydrochemical composition analysis results indicate that the geothermal water in the hot springs is of hydrochemical type HCO3-Ca·Mg. Moreover, the geothermal water has high HBO2 and Na+ concentrations, suggesting protracted water runoff and strong water–rock interactions during its evolution. According to the mineral–water solubility equilibrium and silica geothermometers, it is estimated that the reservoir temperature of the Zulongpu hot spring is 47 °C and other hot springs have much higher reservoir temperatures of 116–130 °C. As indicated by geothermal gradients, annual temperatures, and reservoir temperatures, the geothermal water in Meipu and Qvzika villages has the greatest circulation depth, up to 3600–4300 m, followed by that in Rumei town (3700–4000 m) and Zulongpu village (~1500 m). The 2H-18O isotopic analysis of the geothermal surface water revealed that the geothermal water originates from meteoric water. The recharge elevation was inferred to be ~4700–4900 m. Moreover, the low 3H values (&lt;1 Tu) suggest that the geothermal water is older than 40 years. The PHREEQC inverse simulation results indicated that the variation in the hydrochemical composition of the geothermal water results from the precipitation of chalcedony and dolomite, the absorption of NaX, and the loss of CaX2 during migration and storage.

Spatiotemporal variation characteristics of hourly soil temperature in different layers in the low-latitude plateau of China

Soil temperature change has considerable impact on land surface energy and water balances, and hence on changes in weather/climate, surface/subsurface hydrology, and ecosystems. However, little is known regarding the spatiotemporal variations and influencing factors of changes in hourly soil temperature (depth: 5–320 cm) in low-latitude highland areas. This study analyzed the hourly soil temperature at each hour during 2004–2020 and at 08:00, 14:00, and 20:00 (Beijing Time) during 1961–2020. The results revealed the following. 1) As soil depth increased, average soil temperature increased in autumn and winter, and decreased annually and in spring and summer. It exhibited significant increase during 00:00–23:00 annually, seasonally, and monthly, especially at depths of 40–320 cm during 2004–2020. Average soil temperature increased at 08:00 and decreased at 14:00 and 20:00 with increasing soil depth, but the opposite trend was found annually, seasonally, and monthly at 08:00, 14:00, and 20:00 during 1961–2020. 2) With increasing elevation, average soil temperature decreased at 08:00, 14:00, and 20:00 at depths of 5–20 cm, and showed significant increase trend at 08:00 and 14:00 at depths of 10–20 cm (except at 14:00 at 10-cm depth). 3) At 5-cm depth, the critical accumulated soil temperature of ≥12°C and 14°C extended the potential growing season during 1961–2020. 5) Significant uptrend of hourly soil temperature annually, seasonally, and monthly potentially leads to additional release of carbon to the atmosphere and increased soil respiration, reinforcing climate warming. These findings contribute to better understanding of the variation of shallow soil temperatures and land–atmosphere interactions in low-latitude highland areas.

Thermal storage under an earthen roadway embankment over a permafrost region

Building roadways in permafrost regions is always challenged because both roadway construction and global warming can induce the warming of the underlying soils. A group of permafrost cooling techniques has been employed to cool the embankment, with the focus on dropping the temperature of the underlying permafrost. To this end, understanding the thermal storage in the underlying soils after the embankment construction is critical to adopt the right techniques to drain the soils' heat at the right place. While the non-linear variation of heat absorption with depth in the permafrost under the embankment has been well documented, it remains unknown how to describe this situation mathematically. In this study, we innovatively propose a scalar ∆E to characterize the thermal storage of the soils under an earthen embankment over a permafrost region. It is found that immediately after the embankment was built, the soils at 0–3 m depth are cooled down while those at 3–6 m depth are warmed up. However, the temperature variations of these soils, in shape and in trend, are different from the thermal storage of the soils. The profile of temperature variation versus depth changes continuously, while the profile of thermal storage versus depth varies abruptly at the interfaces of soil layers. The reason is that most heat entering the permafrost stratum is stored in water-rich soils while a limited heat is deposited in water-poor soils. This finding suggests that permafrost cooling techniques shall be considered to drain the thermal storage in the water-rich soils primarily.

Sedimentary, littoral and planktic diatoms show different diversity patterns and assembly mechanisms in mountain lakes of the northern European Alps

This study analysed diversity patterns of sedimentary, littoral and planktic diatoms in 43 mountain lakes in the northern European Alps and identified processes that contribute to these patterns. Linear regression models showed a significant increase of sedimentary α-diversity with lake area and conductivity and a negative trend with increasing elevation, whilst the littoral diatom α-diversity increased significantly with conductivity and lake water temperature. Planktic diatom α-diversity significantly decreased with lake area and depth. August water temperature, total phosphorus, conductivity and lake depth explained a significant part of the variation and were significantly correlated with pairwise β-diversities in the data sets, but spatial and shared effects of space and environment were more important for planktic and littoral diatoms. A null model approach based on assemblages’ dissimilarities revealed that the structure of littoral and planktic assemblages was predominantly stochastic. In contrast, sedimentary diatoms were formed by both deterministic and stochastic processes. Abundant and widespread species contributed a large part to the assemblage β-diversity. The results point to a stronger role of niche assembly in sedimentary than for littoral and planktic diatoms. Dispersal limitation, in turn, is likely to contribute to the spatial patterns and stochastic assembly processes observed for littoral and planktic diatoms.

Depth and temperature drive patterns of spatial overlap among fish thermal guilds in lakes across Ontario, Canada

AbstractAimThe spatial distribution of ectotherms is strongly dependent on the temperature of their environments. In temperate lakes, fishes with different thermal optima can become spatially segregated during summer stratification. This habitat partitioning, or niche complementarity, may play a role in the coexistence of trophically similar species; however, the extent of partitioning is dependent on the resources available within each habitat. Although habitat partitioning of fish thermal guilds has been studied in individual lakes, broad‐scale patterns of spatial overlap and segregation are not yet understood. In this study, we explore the patterns and drivers of spatial overlap among thermal guilds (cold‐, cool‐, and warm‐water) at a broad scale.LocationOntario, Canada.MethodsWe built a multivariate regression tree to explore patterns and environmental drivers of spatial overlap in freshwater fishes across three thermal guilds from 438 lakes.ResultsWe identified five clusters of lakes exhibiting different patterns of spatial overlap among the three thermal guilds. Temperature (growing degree days) and maximum lake depth were strong drivers of the spatial overlap patterns.Main ConclusionsThese findings provide a better understanding of broad‐scale patterns of spatial overlap and allow us to predict how spatial overlap, and ultimately species interactions and competition, may change under a warming climate.

Assessing the Potential Increase in the Energy Storage Density of Subsea Hydro-Pneumatic Accumulators Using Carbon Dioxide in Lieu of Air

Abstract The integration of energy storage systems (ESS) on a large scale is becoming essential to mitigate intermittency issues in power supply from offshore wind farms. This paper deals with an offshore hydro-pneumatic energy storage (HPES) system comprising of a subsea accumulator pre-charged with a compressed gas. The paper applies a simplified thermodynamic model to investigate the potential increase in the energy storage density of the proposed HPES system by replacing air with carbon dioxide (CO2) that is able to undergo a phase change (gas-liquid-gas) during the storage cycle when limiting the peak operating pressure below the critical point. The study is based on a numerical model for simulating the thermodynamics of the entire storage cycle. A sensitivity study is conducted to examine the influence of main operational parameters, primarily the seawater temperature, peak working pressure, and sea depth, on the storage density of the HPES system operating with a dual phase fluid. It is shown that the storage density of HPES accumulators can be increased substantially by using CO2 in lieu of air. The increase in density is found to depend considerably on the seawater temperature and sea depth.

Linkage between the vegetation indices and climate factors over Haryana

Present study was an attempt to study the relationship of Normalized Difference Vegetation Index (NDVI) and Leaf Area Index (LAI) with climatic parameters (maximum temperature, minimum temperature, relative humidity, rainfall, wind speed and aerosol optical depth) over the Indian state of Haryana using MODIS derived vegetation indices on monthly and yearly values for the time period from 2010 to 2020. The values of correlations coefficients of NDVI and LAI with climatic variables varied with the months, the nature of their variation was similar for two indices. During summer season the correlation values were maximum while these were minimum during rainy season. The overall correlation analysis revealed that the rainfall and relative humidity were positively correlated with NDVI and LAI, while the remaining climate variables had negative impact on the NDVI and LAI.

The hydrothermal changes of permafrost active layer and their impact on summer rainfall-runoff processes in an alpine meadow watershed, northwest China

The freezing-thawing variation of permafrost active layer increases the complexity of rainfall-runoff processes in alpine river basins, Northwest China. And alpine meadow is the prominent ecosystem in these basins. This study selected a small alpine meadow watershed in the upper reaches of the Shule River Basin, China. We investigated alpine rainfall-runoff processes, as well as impacts of summer thaw depth of active layer, soil temperature and moisture variation on streamflow based on in-situ observations from July 2015 to December 2020. Some hydrologic parameters or indices were calculated using statistical methods, and impacts of permafrost change on river runoff were assessed using the variable infiltration capacity model (VIC). In the alpine meadow, surface soil (0–10 cm depth) of the active layer starts to freeze in mid-October each year, and begins to thaw in early April. Also, the deeper soil (70–80 cm depth) of the active layer starts to freeze in late October, and begins to thaw in late June. Moisture content in shallow soils fluctuates regularly, whereas deeper soils are more stable, and their response to rainstorms is negligible. During active layer thawing, the moisture content increases with soil depth. In the alpine meadow, vertical infiltration only occurred in soils up to 40 cm deep, and lateral flow occurred in 0–20 and 60–80 cm deep soils at current rainfall intensity. Summer runoff ratios were 0.06–0.31, and runoff floods show lags of 9.5–23.0 h following the rainfall event in the study area. The freeze–thaw process also significantly impacts runoff regression coefficients, which were 0.0088–0.0654 per hour. Recession coefficient decrease negatively correlates with active layer thawing depth in summer and autumn. Alpine river basin permafrost can effectively increase peak discharge and reduce low flow. These findings are highly significant for rainfall–runoff conversion research in alpine areas of inland rivers.

Estimation of Spatial Groundwater Recharge and Surface Runoff in the Gaza Coastal Aquifer Using GIS-Based WetSpass Model

Assessment of the spatial distribution of water recharge and surface runoff is essential for water resource management and planning. This research evaluates spatial distributions of groundwater recharge, surface water flow, and evapo-transpiration for the Gaza coastal aquifer, Palestine in 2020 using the WetSpass model integrated with GIS. The ArcGIS tool is implemented to create grid maps of the WetSpass model data, such as temperature, rainfall, wind velocity, potential evapo-transpiration, soil map, land use, topography, gradient, and water depth. The model generates computerized maps of yearly groundwater recharge, surface water flow, and evapo-transpiration. The WetSpass model's calibration procedures were implemented by manually altering or changing the model parameters already included in the WetSpass model within a predetermined range of values. The simulated results revealed that the average yearly groundwater recharge was 42 mm/year, surface runoff was 38 mm/year and actual evapotranspiration was 268 mm/year. The research findings would help local stakeholders and decision-makers manage groundwater resources in a sustainable and effective manner.