The purpose of this paper is to provide a comprehensive presentation and interpretation of the Ensemble Kalman Filter (EnKF) and its numerical implementation. The EnKF has a large user group, and numerous publications have discussed applications and theoretical aspects of it. This paper reviews the important results from these studies and also presents new ideas and alternative interpretations which further explain the success of the EnKF. In addition to providing the theoretical framework needed for using the EnKF, there is also a focus on the algorithmic formulation and optimal numerical implementation. A program listing is given for some of the key subroutines. The paper also touches upon specific issues such as the use of nonlinear measurements, in situ profiles of temperature and salinity, and data which are available with high frequency in time. An ensemble based optimal interpolation (EnOI) scheme is presented as a cost-effective approach which may serve as an alternative to the EnKF in some applications. A fairly extensive discussion is devoted to the use of time correlated model errors and the estimation of model bias.

The Ensemble Kalman Filter: Theoretical formulation and practical implementation

https://www.ukm.my/ipi/wp-content/uploads/2013/07/70_2002_Consequences-of-climate-change-for-European-agricultural.pdf

Consequences of climate change for European agricultural productivity, land use and policy

Sampling and analysis or visual examination of soil to assess its status and use potential is widely practiced from plot to national scales. However, the choice of relevant soil attributes and interpretation of measurements are not straightforward, because of the complexity and site-specificity of soils, legacy effects of previous land use, and trade-offs between ecosystem services. Here we review soil quality and related concepts, in terms of definition, assessment approaches, and indicator selection and interpretation. We identify the most frequently used soil quality indicators under agricultural land use. We find that explicit evaluation of soil quality with respect to specific soil threats, soil functions and ecosystem services has rarely been implemented, and few approaches provide clear interpretation schemes of measured indicator values. This limits their adoption by land managers as well as policy. We also consider novel indicators that address currently neglected though important soil properties and processes, and we list the crucial steps in the development of a soil quality assessment procedure that is scientifically sound and supports management and policy decisions that account for the multi-functionality of soil. This requires the involvement of the pertinent actors, stakeholders and end-users to a much larger degree than practiced to date.

Soil quality – A critical review

Future trajectories of food prices, food security, and cropland expansion are closely linked to future average crop yields in the major agricultural regions of the world. Because the maximum possible yields achieved in farmers’ fields might level off or even decline in many regions over the next few decades, reducing the gap between average and potential yields is critical. In most major irrigated wheat, rice, and maize systems, yields appear to be at or near 80% of yield potential, with no evidence for yields having exceeded this threshold to date. A fundamental constraint in these systems appears to be uncertainty in growing season weather; thus tools to address this uncertainty would likely reduce gaps. Otherwise, short-term prospects for yield gains in irrigated agriculture appear grim without increased yield potential. Average yields in rainfed systems are commonly 50% or less of yield potential, suggesting ample room for improvement, though estimation of yield gaps for rainfed regions is subject to more errors than for irrigated regions. Several priorities for future research are identified.

/pdf/crop-yield-gaps-their-importance-magnitudes-and-causes-42b9lmuvu3.pdf

Crop yield gaps: their importance, magnitudes, and causes.

The topics addressed in this volume of a continuing series on the soil sciences are soil-water repellency, nutrient transformations in soils amended by green manures, and the physical fractionation of soil and organic matter in primary particle size and density separates.

Advances in Soil Science

The WOFOST simulation model is a tool for analysing the growth and production of field crops under a wide range of weather and soil conditions. Such an analysis is important first to assess to what extent crop production is limited by the factors of light, moisture and macro-nutrients, and second to estimate what improvements are possible. The theoretical concept of a production situation, as modelled by WOFOST, is explained, as is the hierarchy of potential production and water-limited and nutrient-limited production situations in the analysis. The organization of the computer files in the model, the structure of the FORTRAN source program and the available standard sets of data are described briefly. The functions of the most important program sections are discussed. The model can be implemented on many kinds of computers. It can be used on its own, for site­ specific studies of agricultural production potentials. But it can also be coupled to Geographic Information Systems for regional studies, or be used as a data generator for regional agro-economic models. The data on climate, soil and crop, needed for the calculations with WOFOST are specified. However, the general scarcity of comprehensive datasets forms a major constraint for the widespread use of the model in land evaluation. Research (CABO). The version of the model described -- --~~=~~~: ~~;~~i~~~;c;~:~e s~~~~~~A:,~e~~~~:x 14~ 6700 -AA ··~· herej~ ~alled_WQFOST 4.1, which is _the_~'!n~'!rc!. .Y~~i()11

/pdf/wofost-a-simulation-model-of-crop-production-54di1e0eml.pdf

WOFOST: a simulation model of crop production.

https://www.isprs.org/proceedings/XXXVI/7-C50/papers/P28.pdf

Crop model data assimilation with the Ensemble Kalman filter for improving regional crop yield forecasts

According to Stewart (1968), land evaluation is “the assessment of the suitability of land for man’s use in agriculture, forestry, engineering, hydrology, regional planning, recreation, etc.” Many disciplines have contributions to make to land evaluation in its widest sense. The present review focuses on the role of soil science in land evaluation.

Land Evaluation: From Intuition to Quantification

WOFOST version 7.1 is a computer model that simulates the growth and production of annual field crops. All the run options are operational through a graphical user interface named WOFOST Control Center version 1.5 (WCC). WCC facilitates selecting the production level, and input data sets on crop, soil, weather, crop calendar, hydrological field conditions, soil fertility parameters and the output options. The files with crop, soil and weather data are explained, as well as the run files and the output files. A general overview is given of the development and the applications of the model. Its underlying concepts are discussed briefly.

WOFOST 7.1; user's guide for the WOFOST 7.1 crop growth simulation model and WOFOST Control Center 1.5

https://www.ukm.my/ipi/wp-content/uploads/2013/07/11.2012Assessing-climate-change-effects-on-European-crop-yields-using-the-Crop-Growth.pdf

C.A. van Diepen

Papers

WOFOST: a simulation model of crop production.

Crop model data assimilation with the Ensemble Kalman filter for improving regional crop yield forecasts

Land Evaluation: From Intuition to Quantification

WOFOST 7.1; user's guide for the WOFOST 7.1 crop growth simulation model and WOFOST Control Center 1.5

Assessing climate change effects on European crop yields using the Crop Growth Monitoring System and a weather generator