Infering meteorological information at different scales from several sources of data

Description

One of the major challenges to monitor, foresee and anticipate the landscape evolution is tounderstand the climate change geographical effects (Aspinal, 2012) on different, especially local,scales (Martin et al., 2013; Barry & Blanken, 2016). For instance, measuring the evolution oftemperature is possible, one the one hand, using a series of (often spatially accurate, but irregular)sensors spread over a given territory (e.g. a watershed). On another hand, we have today a largeaccess to climate models, providing meteorological projections at a certain (generally coarse, butregular) spatial and temporal granularity. From both those types of data, scientist can inferinformation at different (nested) scales, applying upscaling (by spatial data aggregation) ordownscaling (assuming some disaggregation hypothesis) processes.This work deals with this issue: how can we infer a reliable spatial information from meteorologicaldata provided from two different levels and methodologies? More precisely, can we provide relevantestimations on climate drivers at different scales, in the particular case of meteorological data(illustrated by temperature)? To answer to these two questions, we face two problems: (i) how tocombine these two sources of data (ii) and how to deal with the Ecological Effect (Holt, 1996; King,1997) or the Modifiable Areal Unit Problem (Openshaw, 1984), that may strongly impair theestimate reliability and usability to forecast the likely climate landscapes for the future?In this work, we present recent results obtained by studying temperatures measurements from a set ofmeteorological stations and the ALADIN model grid on long time series in the French southernregion of Provence Alpes Côte d'Azur. Using those two sources of data, we aggregatetemperature values and observe their variation through different administrative territorial partitions(somehow French delineations under the regional scale NUTS2 : "départements", "arrondissements","cantons", "communes" and "EPCI", i.e. groups of communes).This leads us to draw what we call "scalograms" which plot average or mediantemperatures according to the different nested levels of scale. Those are provided for both thegridded ALADIN model and the series of local meteorological stations, and compared. We noticesome differences in the estimations that show the necessary caution to pay for generatingmeteorological data using a multiple scale approach. A method, published a few year ago, based onspatial random permutation (Josselin et al., 2008) and generalized to any data (Josselin et al., 2023),is applied on this kind of climate data to mitigate the change of support problem and to improve thedata reliability to potentially characterize more accurately the landscapes at different scales.ReferencesAspinal R. (Ed.). (2012). Geography of climate change. Routeledge, Taylon Fancis.Barry R. G., Blanken P. D. (Eds.). (2016). Microclimate and local climate. Cambridge University Press.Holt D., Steel D., Tranmer M., Wrigley N. (1996). Aggregation and ecological effects in geographically baseddata. Geographical Analysis, vol. 28, p. 244-261.Josselin D., Mahfoud I., Fady B. (2008). Impact of a change of support on the assessment of biodiversity withshannon entropy. In Spatial Data Handling, SDH'2008", pp. 109-131. Montpellier, June, 23-25.Josselin D., Blanke D., Coulon M., Boulay G., Casanova Enault L., Peris A., Le Brun P., Lecourt T. (to bepublished, 2023). Incertitudes liées aux échelles d'estimation des prix immobiliers. In L'imperfection desdonnées géographiques. Tome 2. (Eds: M. Batton-Hubert, E. Desjardin, F. Pinet), ISTE-WileyKing G. (1997). A solution to the ecological inference problem. Reconstructing individual behaviour fromaggregate data. Princeton University Press.Martin N., Carrega P., Adnès C. (2013). Downscaling à fine résolution spatiale des températures actuelles etfutures par modélisation statistique des sorties ALADIN-climat sur les Alpes-Maritimes (France).Climatologie, Association internationale de climatologie, pp.51-72.Openshaw S. (1984). The modifiable areal unit problem. Norwich: Geo Books, CATMOG 38.

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