Precipitation In Semi-arid Regions Research Articles

Performance Assessment of GPM IMERG Products at Different Time Resolutions, Climatic Areas and Topographic Conditions in Catalonia

Quantitative Precipitation Estimates (QPEs) from the Integrated Multisatellite Retrievals for GPM (IMERG) provide crucial information about the spatio-temporal distribution of precipitation in semiarid regions with complex orography, such as Catalonia (NE Spain). The network of automatic weather stations of the Meteorological Service of Catalonia is used to assess the performance of three IMERG products (Early, Late and Final) at different time scales, ranging from yearly to sub-daily periods. The analysis at a half-hourly scale also considered three different orographic features (valley, flat and ridgetop), diverse climatic conditions (BSk, Csa, Cf and Df) and five categories related to rainfall intensity (light, moderate, intense, very intense and torrential). While IMERG_E and IMERG_L overestimate precipitation, IMERG_F reduces the error at all temporal scales. However, the calibration to which a Final run is subjected causes underestimation regardless in some areas, such as the Pyrenees mountains. The proportion of false alarms is a problem for IMERG, especially during the summer, mainly associated with the detection of false precipitation in the form of light rainfall. At sub-daily scales, IMERG showed high bias and very low correlation values, indicating the remaining challenge for satellite sensors to estimate precipitation at high temporal resolution. This behaviour was more evident in flat areas and cold semi-arid climates, wherein overestimates of more than 30% were found. In contrast, rainfall classified as very heavy and torrential showed significant underestimates, higher than 80%, reflecting the inability of IMERG to detect extreme sub-daily precipitation events.

Spatio-temporal changes in the speed of canopy development and senescence in temperate China.

China has been suggested to be the country with the largest vegetation greenness over the last four decades. In this study, we investigated the change in the speed of canopy development and senescence as well as its linkage with climate at monthly scale across temperate China, using satellite-derived Normalized Difference Vegetation Index (NDVI) data from 1982 to 2015. A significant increase in mean monthly NDVI occurred across all growing-season months except June and November, but this greening trend was mainly contributed by the faster speed of canopy development in April and the slower speed of canopy senescence in October. The average of VNDVI (the difference in NDVI between 2 consecutive months) over temperate China is significantly increased only in April (7.75 × 10-4 year-1 , p < .05) and October (4.98 × 10-4 year-1 , p < .05). In contrast, VNDVI in November is significantly decreased, indicating an increasing trend in the magnitude of leaf fall in the last month of the growing season due to both increase in season maximum greenness and slower canopy senescence in October. We also found clear seasonal differences in the correlations between VNDVI and climatic factors, especially temperature. In April and October, the correlations between VNDVI and temperature were generally positive, while they were negative in June. VNDVI in spring (early growing season) and summer (middle growing season) was also positively correlated with precipitation in semiarid regions. Such seasonally distinct climatic controls on VNDVI should be considered in modelling vegetation responses to climate change. Overall, our findings can help quantify the contribution of different climatic drivers on the shifts in canopy development and senescence and better elucidate the change in vegetation greenness under future climate change.

Impacts of Cumulus Parameterizations on Extreme Precipitation Simulation in Semi-Arid Region: A Case Study in Northwest China

In the context of climate change, extreme precipitation in semi-arid region happens frequently. How well models simulate extreme precipitation in semi-arid region remains unclear. Based on a WRF v4.3 simulation of a rainstorm event that occurred in Qingyang, China on 21 July 2019, applying Kain–Fritsch (KF), Grell–Devenyi (GD) and Bullock–Wang (BW) schemes, the impacts of different cumulus parameterizations on extreme precipitation simulations in semi-arid region were analyzed, and the possible causes of precipitation biases were explored. The results showed that the WRF with the three schemes essentially reproduced the location and structure of precipitation, but the intensity of precipitation in the central region was underestimated. Based on the structure-amplitude-location (SAL) method, the KF scheme exhibited better performance in precipitation simulation than the other two schemes, while there were significant intensity and location deviations of rain band occurrence between simulations using the GD, BW schemes and observations. Convection simulation using the GD and BW schemes was less effective than that using the KF scheme, compared to the observations. As a result, the GD and BW schemes simulated a larger geopotential height at 500 hPa over Qingyang and weaker upper-level low troughs than simulations using the KF scheme. This led to simulation of less water vapor transport into the front of the trough, resulting in a deficit in simulated precipitation. The study results highlight the impacts of convection on large-scale atmospheric circulation linked to extreme precipitation in semi-arid region.

The Role of Moisture Conveyor Belts for Precipitation in the Atacama Desert

AbstractIn the hyperarid Atacama Desert in northern Chile, rare precipitation events can leave long‐lasting geomorphological traces and have strong impacts on biota. While moisture conveyor belts (MCBs) and atmospheric rivers (ARs) have been associated with extreme precipitation in semiarid regions, their role for the Atacama Desert has not been previously investigated. This study reveals that about four MCBs per year make landfall in the Atacama Desert. According to simulated precipitation, 40–80% of the total precipitation between the coast and the Andean foothills is associated with MCBs. A case study reveals an elevated moisture transport decoupled from the maritime boundary layer, which is generalized by a composite analysis. Back trajectories reveal the Amazon Basin as the main source of moisture. MCB landfall times are derived from the AR catalog by Guan and Waliser (2015), https://doi.org/10.1002/2015jd024257. Implications of the results on paleoclimate reconstructions are discussed.

Comparing overland flow processes between semiarid and humid regions: Does saturation overland flow take place in semiarid regions?

Two main processes of runoff are commonly thought to take place in a drainage basin: infiltration-excess overland flow, known also as Hortonian overland flow (HOF), and saturation overland flow (SOF). While HOF mainly takes place in arid and semiarid regions once the infiltration capacity of the upper skin of the soil (usually ~1 mm thick) is surpassed, SOF may takes place in wet humid and subhumid climates. SOF takes place once the groundwater table reaches the surface (mainly close to the stream channel), or due to an impermeable subsurface soil layer. Despite the low precipitation in semiarid regions, a number of publications advocated the occurrence of SOF also in semiarid regions, subsequently underplaying the centrality of biocrusts to effectively generate runoff. These publications are mainly based on moisture measurements that were conducted with dielectric-based sensors. In the present work, it will be argued that: (a) the amount and duration of the rain cannot possibly result in SOF, (b) the location of the alleged SOF, as reported by some publications (at the up- or mid-slope), is unlikely to facilitate SOF, (c) the likelihood that the electrical pulses produced by the dielectric-based sensors will distinguish between completely saturated and nearly saturated conditions is low, (d) in certain occasions even when the moisture content, as detected by these sensors, was slightly below saturation, the authors tended to assume that the soil was saturated, (e) while claiming that the subsurface soil layer reached saturation, the upper layer of the soil (where overland flow takes place) was occasionally reported to remain below saturation, (f) no supportive evidence for the occurrence of SOF or even subsurface flow was provided, such as visible wet belts with dense vegetation. It is therefore concluded that the occurrence of SOF in semiarid regions should be cautiously considered and re-examined.

Supplemental irrigation strategy for improving grain filling, economic return, and production in winter wheat under the ridge and furrow rainwater harvesting system

The plastic-covered ridge and furrow rainwater harvesting (RFRH) system has been used widely to enhance crop productivity in the semiarid regions of China. We conducted a field study during 2015–2017 where the RFRH method was combined with deficit irrigation to decrease the irrigation water usage and improve the crop water productivity (CWP) and irrigation water productivity (IWP). Under the RFRH system, the amount of irrigation was reduced by half compared with that under traditional flat planting (TF) with border irrigation due to the effects of precipitation harvesting. Half of the deficit irrigation was supplied before wintering and the remaining half at the jointing stage. The following eight treatments were tested: RFRH system with 75 mm deficit irrigation (R75), 37 mm irrigation (R37), 18 mm irrigation (R18), and 0 mm irrigation (R0); TF cultivation with 150 mm irrigation (F150), 75 mm irrigation (F75), 37 mm irrigation (F37), and 0 mm irrigation (F0). The results showed that the irrigation volume doubled under conventional border irrigation but the soil water storage was greater under RFRH with deficit irrigation. The R75 treatment resulted in significantly greater soil water storage, reduced evapotranspiration (44.2%), and a higher grain yield (14.6%), thereby increasing CWP (64.8%), ICWP (irrigation crop water productivity) (44.2%), and IWP (57.0%) compared with F150. R75 improved the biomass per plant, leaf area index, and net income for farmers (by 17.5%) compared with F150. Thus, we recommend R75 for decreasing the irrigation water usage and increasing the effective consumption of precipitation in semiarid regions.

Chemo-isotopes (18O &2H) signatures and HYSPLIT model application: Clues to the atmospheric moisture and air mass origins

The first ever systematic study on spatio-temporal variation of the chemo-isotopic compositions of the precipitation in Iran was carried out in a hydrological year (2016–2017) at 7 sites located in Bojnourd area, northeast of Iran. The main aims were to determine the moisture and air mass sources and, in particular, to evaluate the effect of atmospheric conditions on isotope compositions. The isotopic value of the precipitation fluctuates seasonally with higher values in summer and lower values in winter at the all sites. Stable isotope values of the precipitation samples within the local scale resulted a Bojnourd meteoric water line (BMWL): δD = 6.4 × δ18O+1.2 (R2 = 0.93, n = 75), with a lower slope and intercept than the global meteoric water line (GMWL) due to isotope kinetic fractionation effects during precipitation in semi-arid region with lower humidity. The air temperature can be suggested as the main controlling factor that impacts the stable isotope compositions of precipitation in the study area. The large rainfall events totally displayed the highest slope, intercept and d-excess values nearly similar to the snowfall samples, indicating the re-evaporation effects on the low rainfall amounts. Precipitations during summer season (Jun–August) with higher isotopes and lower d-excess values mainly originated from the polar and Caspian Sea air moistures. While, moisture contributing to high d-excess and low isotope precipitation during January was mainly transported by the Mediterranean air moisture. The air-mass trajectories that affect the precipitation in autumn (September–December) and spring (March–May) displayed multiple sources, originating from the polar, Mediterranean and Caspian Sea air moistures. Trajectory analysis by HYSPLIT modeling allowed the association of moisture sources with the isotopic compositions of the precipitation. Based on the sea salt contribution for Na+ and Cl−, a sea effect is recognized especially from Caspian Sea and Mediterranean region, despite the long distance at the present study. The correlation between EC and the ions indicate that ion compositions in the precipitation and atmosphere of the study area are mainly effected by dust of soil and sea salt and to some extent from secondary evaporation during rainfall. The hydrochemical investigations confirmed the air masses trajectories which resulted from the isotopic characteristics.

Changing precipitation exerts greater influence on soil heterotrophic than autotrophic respiration in a semiarid steppe

Future precipitation change is anticipated to have a profound influence on ecosystem carbon (C) cycling, especially soil respiration, the largest C flux from the terrestrial ecosystem to the atmosphere. Due to different substrate sources and biological processes, the heterotrophic (SRh) and autotrophic (SRa) components of soil respiration (SRtot) may respond to changing precipitation in different ways. Determining the differential responses of SRh and SRa to precipitation will facilitate our evaluation of soil C storage and stability under future precipitation change. Here, a 3-year precipitation manipulation experiment with 5 levels of precipitation (±60%, ±30% and ambient growing season precipitation) was conducted in a semiarid steppe to determine the influence of precipitation on soil respiration. Results showed that SRtot increased nonlinearly with increasing water supply, in which, SRh increased much more than SRa. Consequently, the ratio of SRh to SRtot was enhanced significantly with increasing precipitation, i.e., from 41% to 62% as precipitation increased from 122 mm to 408 mm. Structural equation modeling analysis indicated that changes in SRh and SRa were predominated by the soil water content (SWC) and plant growth, respectively. The stronger effects exerted by changes in precipitation on SWC compared with plant growth contributed to the greater change in SRh than in SRa. Additionally, SRa exhibited a higher temperature sensitivity than SRh. Thus, the increased soil temperature in the drought treatments had greater influence on SRa than SRh, and greatly offset the influence of drought stress on SRa, leading to the smaller change in SRa compared with SRh. Our study highlights the different responses of the two soil respiration components to changing precipitation. These results indicate that future increases in precipitation in semiarid regions will increase soil heterotrophic respiration which may accelerate the turnover of soil C, and further affect the stability of soil C stock.

Climatic Effects on Quality Parameters and Their Relationships of Bread Wheat Genotypes (Triticum aestivum L.) Grown under Semi-arid Region

Aims: This study was conducted to determine climatic effects to quality parameters of bread wheat genotypes grown in the semi-arid region.&#x0D; Study Design: The experiment was carried out in a randomized complete block design with three replications. Thirty-three bread wheat genotypes (Triticum aestivum L.) were grown in a field trial and kernel samples analyzed for thousand kernel weight, test weight, protein content, wet gluten, dry gluten and SDS-sedimentation value.&#x0D; Place and Duration of Study: The research was carried out during the 2008 and 2009 growing seasons at Sanliurfa, Turkey.&#x0D; Methodology: For analyses 20 main spikes that contained fully developed kernels were chosen randomly from each plot and taken to the laboratory for analyses. The nitrogen content of kernels was determined using the Kjeldahl method and the result was multiplied by the factor 5.7 to calculate the protein content of kernels. Test weight and Sodium Dodecyl Sulphate (SDS)-sedimentation values were determined using standard procedures. Wet and dry gluten values were determined using a glutomatic system after separating gluten from the soluble starch and protein fractions.&#x0D; Results: Genotypes were significant (P ≤ 0.01) for all tested characteristics. Thousand kernel weight ranged from 25.8 to 42.3 g, test weight from 73.7 to 81.7 kg hl-1, protein content from 9.7 to 14.8%, wet gluten from 28.5 to 42.2%, dry gluten from 9.4 to 14.1% and SDS-sedimentation value from 19 to 39 ml. Bezostaya-I, Kutluk-94, Altay-85, Harmankaya-99, Lirasa, Kirgiz-95 and Dagdas-94 genotypes had the best quality among tested genotypes in the semi-arid climatic conditions. Protein content was positively correlated with wet gluten, dry gluten and SDS-sedimentation value, respectively. Relationships were significant between wet gluten and both dry gluten and SDS-sedimentation value. A positive significant correlation was found between thousand kernel weight and SDS-sedimentation value and between dry gluten and SDS-sedimentation value.&#x0D; Conclusion: Protein content, wet and dry gluten and SDS-sedimentation value were affected by climatic conditions of semi-arid region. Protein content, wet and dry gluten value were high but SDS-sedimentation value were low due to high temperature and low precipitation in semi-arid region.

Climatic Effects on Quality Parameters and Their Relationships of Bread Wheat Genotypes (Triticum aestivum L.) Grown under Semi-arid Region

Aims: This study was conducted to determine climatic effects to quality parameters of bread wheat genotypes grown in the semi-arid region.&#x0D; Study Design: The experiment was carried out in a randomized complete block design with three replications. Thirty-three bread wheat genotypes (Triticum aestivum L.) were grown in a field trial and kernel samples analyzed for thousand kernel weight, test weight, protein content, wet gluten, dry gluten and SDS-sedimentation value.&#x0D; Place and Duration of Study: The research was carried out during the 2008 and 2009 growing seasons at Sanliurfa, Turkey.&#x0D; Methodology: For analyses 20 main spikes that contained fully developed kernels were chosen randomly from each plot and taken to the laboratory for analyses. The nitrogen content of kernels was determined using the Kjeldahl method and the result was multiplied by the factor 5.7 to calculate the protein content of kernels. Test weight and Sodium Dodecyl Sulphate (SDS)-sedimentation values were determined using standard procedures. Wet and dry gluten values were determined using a glutomatic system after separating gluten from the soluble starch and protein fractions.&#x0D; Results: Genotypes were significant (P ≤ 0.01) for all tested characteristics. Thousand kernel weight ranged from 25.8 to 42.3 g, test weight from 73.7 to 81.7 kg hl-1, protein content from 9.7 to 14.8%, wet gluten from 28.5 to 42.2%, dry gluten from 9.4 to 14.1% and SDS-sedimentation value from 19 to 39 ml. Bezostaya-I, Kutluk-94, Altay-85, Harmankaya-99, Lirasa, Kirgiz-95 and Dagdas-94 genotypes had the best quality among tested genotypes in the semi-arid climatic conditions. Protein content was positively correlated with wet gluten, dry gluten and SDS-sedimentation value, respectively. Relationships were significant between wet gluten and both dry gluten and SDS-sedimentation value. A positive significant correlation was found between thousand kernel weight and SDS-sedimentation value and between dry gluten and SDS-sedimentation value.&#x0D; Conclusion: Protein content, wet and dry gluten and SDS-sedimentation value were affected by climatic conditions of semi-arid region. Protein content, wet and dry gluten value were high but SDS-sedimentation value were low due to high temperature and low precipitation in semi-arid region.

Landscape Patterns Affect Precipitation Differing across Sub-climatic Regions

Assessment of the impacts of landscape patterns on regional precipitation will help improve ecosystem management and strategies for adaption to global changes. This study aimed to identify the key landscape metrics that affect precipitation across three sub-climatic regions in Inner Mongolia, China, using 266 landscape metrics and daily precipitation data from 38 weather stations for 1995, 2000, 2005, and 2015. Pearson correlation, stepwise linear regression, and Redundancy analysis were used to identify the contributions of landscape patterns to local precipitation in each sub-climatic region. Three-year datasets were used for model development and a one-year data set was used for validation. It was found that the contribution of landscape patterns is higher than that of climatic variations in semi-arid or humid regions. The Core Area Coefficient of Variance (CACoV) of grasslands and Landscape Area (TLA) in non-irrigated croplands have a negative relationship with precipitation in arid regions. Further, the Total Core Area Index (TCAI) of grasslands has a negative correlation with precipitation, while the area proportion (C%LAND) in waters has a significant positive relationship with precipitation in semi-arid regions. Additionally, the Mean Core Area (MCA), Core Area (CA), and Core Area Standard Deviation (CASD) of grasslands and Total Core Area Index (TCAI) of waters are negatively related to precipitation in humid regions. Suitable land use configuration and composition, especially the proportion of grasslands and waters, should be considered in ecosystem management for alleviating the possible harmful effects due to climate change.

Change in Soil Organic Carbon after Five Years of Continuous Winter Wheat or Switchgrass

Core Ideas Soil carbon sequestration under switchgrass depends on precipitation in semiarid regions. Changes in soil C were limited to the surface soil (15 cm) under switchgrass. Switchgrass and continuous winter wheat had similar biomass and soil carbon. Perennial grasses have been promoted to supply cellulose for ethanol production but possible consequences on soil organic carbon (SOC) should be assessed before adoption in a given region. Specific objectives were to (i) compare aboveground biomass C production and depth distribution of SOC content of continuous winter wheat (Triticum aestivum L.) and switchgrass (Panicum virgatum L.), (ii) determine the contribution of switchgrass to SOC, and (iii) characterize soil C inventories under each crop across a wide range of precipitation regimes. A 6‐yr (2008–2013) field study with winter wheat and switchgrass ‘Blackwell’ was conducted in northeastern Oregon. Solid set sprinkler irrigation was used to create a productivity gradient of low, medium, and high precipitation levels. The contribution of switchgrass to SOC was identified with δ13C measurements. Winter wheat had significantly higher 5‐yr‐average aboveground biomass C production than switchgrass across precipitation levels and winter wheat under high precipitation produced significantly higher aboveground biomass C than medium and low precipitation. After 5‐yr of cropping, SOC accrual in the 0‐ to 15‐cm depth was significantly higher under winter wheat than switchgrass in each precipitation regime. Results of δ13C indicated switchgrass contributed 7.9, 8.5, and 12.9% to profile SOC at low, medium, and high precipitation levels. Soil organic carbon in dry cropland is resistant to a shift in crop species. Switchgrass does not increase SOC more than continuous winter wheat in dry cropland of the semiarid Pacific Northwest.

Response of Soil Respiration to Extreme Precipitation in Semi-arid Regions

Evaluating the response of soil microbial respiration to extreme precipitation event is significant for a better understanding about the influence of the change of precipitation regime on soil carbon cycling under global warming. A simulated experiment of extreme precipitations was conducted during the rainy season (July-September 2015) in the Changwu State Key Agro-Ecological Station, Shaanxi, China. The treatments consisted of three total precipitations in rainy season (600 mm, 300 mm, and 150 mm) and two precipitation regimes (10 mm, 150 mm; P10, P150). Soil microbial respiration varied differently in the same single rainfall event among three precipitations. The variation coefficient of soil microbial respiration under 600 mm total precipitation was 36% (P150) and 33% (P10), and 28% and 22% under 300 mm total precipitation, 43% and 29% under 150 mm total precipitation. Under 600 mm total precipitation, the cumulative soil microbial respiration under P150 was 20% less than that under P10; however, the cumulative soil respiration of P150 under 150 mm total precipitation was 22% more than that under P10; and there was no significant difference between P10 and P150 under 300 mm total precipitation. Therefore, the duration in soil water stress must be considered to estimate soil microbial respirations under extreme precipitations.

The Analysis of Spring Precipitation in Semi-Arid Regions: Case Study in Iran

In this study, Zanjan from Iran has been chosen from among all the semi-arid regions of world, which has Synoptic station and statistical data since 1955. Spring and monthly precipitations are also provided in the period of 1956-2005. First, all data has been controlled by double mass method with the help of adjacent stations, and then it was normalized by the box-cox transformations method. The global SPI index was calculated for all months and spring, also drought and wet periods were determined and finally compared. In the drought category view, spring months have represented the great similarities. The moving averages are represented all months and spring’s precipitations such as three years, five years, seven years and nine years are shown. Statistical period was observed and analyzed based on five periods of ten years, and results precipitation with more than 5mm and 10mm has gradually decreased on April. However the number of days with precipitation has increased. The calculated spring precipitations and all of the atmospheric factors represented the dependence of this model to maximum average of spring temperature and relative humidity of spring and winter by the use of multi variable regression method. The predicted precipitation of spring also showed the gradual decline of precipitation in the next 30 years by the arima model.

Complexity and predictability of daily precipitation in a semi-arid region: an application to Ceará, Brazil

Abstract. Complexity and predictability of daily precipitation in a tropical semi-arid region (Ceará State, Brazil) is assessed by applying entropy concepts. Precipitation regimes in that region depend on several dynamical forcings, the most important being the displacement and activity of the Inter-tropical Convergence Zone in the Atlantic Ocean. Topography is another important factor that influences the spatial distribution of rainfall in the region. A hierarchical approach based on sequences of events of different lengths is used to estimate complexity of daily precipitation records. It is shown that precipitation in Ceará exhibit more random than periodic sequences, which indicates a large degree of complexity. Nevertheless, there is indication of potentially inherent rules in the precipitation time-series that could ultimately improve prediction on time-scales between 9–11 days. It is suggested that synoptic-scale disturbances (1–8 days) represent important sources of rules in the precipitation regimes in this region.

Simulated climate and biomes of Africa during the late quaternary: comparison with pollen and lake status data

New compilations of African pollen and lake data are compared with climate (CCM1, NCAR, Boulder) and vegetation (BIOME 1.2, GSG, Lund) simulations for the last glacial maximum (LGM) and early to mid-Holocene (EMH). The simulated LGM climate was ca 4°C colder and drier than present, with maximum reduction in precipitation in semi-arid regions. Biome simulations show lowering of montane vegetation belts and expansion of southern xerophytic associations, but no change in the distribution of deserts and tropical rain forests. The lakes show LGM conditions similar or drier than present throughout northern and tropical Africa. Pollen data indicate lowering of montane vegetation belts, the stability of the Sahara, and a reduction of rain forest. The paleoenvironmental data are consistent with the simulated changes in temperature and moisture budgets, although they suggest the climate model underestimates equatorial aridity. EMH simulations show temperatures slightly less than present and increased monsoonal precipitation in the eastern Sahara and East Africa. Biome simulations show an upward shift of montane vegetation belts, fragmentation of xerophytic vegetation in southern Africa, and a major northward shift of the southern margin of the eastern Sahara. The lakes indicate conditions wetter than present across northern Africa. Pollen data show an upward shift of the montane forests, the northward shift of the southern margin of the Sahara, and a major extension of tropical rain forest. The lake and pollen data confirm monsoon expansion in eastern Africa, but the climate model fails to simulate the wet conditions in western Africa.