Assessment of EnKF Data Assimilation of Satellite Derived Soil Moisture Over the Indian Domain with the Noah Land Surface Model

Land Surface Models (LSMs) are typically forced with observed precipitation and surface meteorology and hence the soil moisture estimates obtained from LSM do not reflect the contribution of irrigation to the soil moisture estimates. However, the satellite retrievals of soil moisture estimates do register the signature of the irrigation effects. It is suggested that the soil moisture estimates obtained from LSM may reflect the role of irrigation if they are assimilated with soil moisture estimated from satellites. The present study evaluates the improvement of soil moisture estimates obtained from Noah LSM by ingesting them with the satellite derived Advanced Scatterometer (ASCAT) soil moisture retrievals over the Indian domain for the year 2012. The above ingesting of soil moisture estimates is performed using the Land Information System (LIS). The improved soil moisture estimates are validated with the in-situ India Meteorological Department (IMD) soil moisture observations and also with the high-resolution Indian Monsoon Data Assimilation and Analysis (IMDAA) regional reanalysis data. The percentage of grid points over the Indian domain where the improvement parameter shows positive values are 59.14% (winter), 69.17% (pre-monsoon), 43.59% (monsoon), and 77.53% (post-monsoon). Furthermore, the forecast impact parameter also indicates the positive impact of data assimilation. Also, 12 of the 22 stations show reduced RMSE soil moisture error after data assimilation is performed while only 6 of the 22 stations show higher correlation coefficient in soil moisture without data assimilation, when validated with the in-situ IMD soil moisture observations. The study has also evaluated the irrigation impact of ASCAT in the assimilated soil moisture using triple collocation (TC) method. For the TC analysis, the model based Global Land Data Assimilation System (GLDAS)Catchment Land Surface Model (CLSM), and MERRA (Modern-Era Retrospective analysis for Research and Applications) Land data set together with soil moisture model outputs with and without ASCAT assimilation are used to calculate the error and correlation coefficient of each of the two set of triplets. The results of the TC analysis further conclusively shows the positive impact of irrigation effects in the ASCAT assimilated soil moisture model output.

Modeling irrigation effects on the regional climate in the "Greater Alpine Region" using a newly developed parameterization

<p><span>Irrigation is a common </span><span>land use </span><span>practice to adapt agriculture to unsuitable climatic conditions. It is highly relevant to ensure food production. Due to the growing population and its food demand in the future, as well as due to climate change, the irrigated area</span><span>s</span> <span>are</span><span> expected to increase </span><span>globally</span><span>. Therefore, it is important to understand the effects of irrigation on the climate system. Irrigation of cropland alters the biogeophysical properties of the land surface and the soil. Due to the land-atmosphere interactions, these alterations </span><span>have the potential to</span><span> affect the atmosphere directly or through feedback processes. Various studies point out that the effects of irrigation, like temperature reduction, are particularly pronounced on local to regional scales where they bear a mitigation potential to regional climate change. </span></p><p><span>This study aims to investigate the effects of irrigation on the regional climate. To model these effects, we developed and implemented a new flexible irrigation parameterization into the regional climate model REMO. In our setup, REMO is interactively coupled to the mosaic-based vegetation module iMOVE, enabling the calculation of irrigation effects and feedbacks on land, vegetation, and atmosphere. Multiple simulations for specific climatic conditions with </span><span>and without </span><span>the </span><span>new</span><span> irrigation parameterization are conducted on 0.11° resolution for the ”Greater Alpine Region“, which includes some of Europe‘s most intensively irrigated areas like the Po valley in Northern Italy. The differences between these simulations are analyzed to identify and quantify irrigation effects on atmospheric processes. </span></p><p><span>The </span><span>new irrigation parameterization will be introduced and the</span><span> analysis </span><span>of the irrigation effects</span> <span>on the regional climate in the “Greater Alpine Region” </span><span>will be presented. </span></p>

Untangling irrigation effects on maize water and heat stress alleviation using satellite data

Irrigation has important implications for sustaining global food production, enabling crop water demand to be met even under dry conditions. Added water also cools crop plants through transpiration; irrigation might thus play an important role in a warmer climate by simultaneously moderating water and high temperature stresses. Here we use satellite-derived evapotranspiration estimates, land surface temperature (LST) measurements, and crop phenological stage information from Nebraska maize to quantify how irrigation relieves both water and temperature stresses. Our study shows that, unlike air temperature metrics, satellite-derived LST detects significant irrigation-induced cooling effect, especially during the grain filling period (GFP) of crop growth. This cooling is likely to extend the maize growing season, especially for GFP, likely due to the stronger temperature sensitivity of phenological development during this stage. The analysis also suggests that irrigation not only reduces water and temperature stress but also weakens the response of yield to these stresses. Specifically, temperature stress is significantly weakened for reproductive processes in irrigated crops. The attribution analysis further suggests that water and high temperature stress alleviation contributes to 65 % and 35 % of yield benefit, respectively. Our study underlines the relative importance of high temperature stress alleviation in yield improvement and the necessity of simulating crop surface temperature to better quantify heat stress effects in crop yield models. Finally, untangling irrigation effects on both heat and water stress mitigation has important implications for designing agricultural adaptation strategies under climate change.

Shade and Irrigation Effects on Growth, Flowering, Pod Yields and Cacao Tree Survival Following 5 Years of Continuous Dry Season Irrigation

The effects of plantain shade and dry season irrigation on the growth, field survival, flowering and pod production of cacao was investigated. Treatments were a 2 by 2 factorial combinations of shade regimes (Unshaded/open sun and shaded) and irrigation intervals (5-day and 10-day intervals) arranged in a split-plot design. There was an unirrigated but shaded control. The shade regimes constituted the main plot while irrigation intervals were the sub-plot treatments. The growth, dry season survival, flowering and pod/bean yield characters of cacao were enhanced in the unshaded (open sun) compared with the shaded plants. The open sun treatment combined with 5-day irrigation produced the largest canopy development, flowering and pod production compared with shading-irrigation combinations. The shade-irrigation ameliorated microclimate and enhanced growth and development, flowering and uniform fruiting/pod production and total bean yield and reduced dry season mortality (whole tree death, branch and twig dieback). For the non-irrigated but shaded cacao, about 30% dry season mortality (branch and twig dieback) were obtained. Air temperatures within the cacao field were highest for open sun cacao followed by moderate and dense shade respectively. Flowers were more profuse for unshaded (open sun) cocoa compared with the shaded while the yield and yield components of cacao for each harvest dates and total pod and bean yields were significantly different between the unshaded and shaded cacao regimes. Trees that were irrigated at 5-day intervals produced significantly (P < 0.05) higher LAI, branching, flowers and pods compared with those irrigated at 10-day intervals. The 5-day irrigation interval significantly increased percentage of trees bearing flowers and pods, and produced larger number, and heavier pods and beans compared with the 10-day interval. The drip irrigation strategy adopted ameliorated dry season terminal drought (hydrothermal stresses) in cacao. This is a veritable tool to scale up growth, survival, establishment and flower/pod production.