Harmonization of GEOV2 fAPAR time series through MODIS data for global drought monitoring.

The temporal consistency of the fAPAR GEOV2 full time series (constituted by data derived from SPOT-VGT1/2 and PROBA-V) is analyzed against the single-sensor MODIS dataset, with a particular focus on the most recent fAPAR anomalies (z-scores) produced from PROBA-V in the period 2014-2017. The intercomparison highlights a systematic overestimation of GEOV2 fAPAR z-scores when compared to MODIS fAPAR, likely related to the observed positive bias (over 90% of the domain) in the PROBA-V vs. SPOT-VGT1/2 relationship. A simple two-step harmonization procedure has been proposed to remove this discrepancy, based on two separate linear corrections of SPOT-VGT1/2 (2001-2013) and PROBA-V (2014-2017) data with respect to MODIS, followed by a time lag correction. The harmonized GEOV2 time series preserves the overall dynamic of fAPAR, while removing the sensor bias and improving the consistency with MODIS data. The fAPAR anomalies from the harmonized GEOV2 time series provide unbiased estimates of z-scores that are overall well correlated (R = 0.55 ± 0.25) with the MODIS fAPAR anomalies.

[Aneurysm of the popliteal vein. A rare cause of recurrent pulmonary embolism]. / L'anévrysme de la veine poplitée. Une cause rare d'embolie pulmonaire à répétition.

Popliteal vein aneurysm, a rarely observed, apparently benign lesion may nevertheless be the cause of disabling pulmonary emboli. Two personal cases and 13 reported in the literature are reviewed. Detected during phlebography of lower limbs during investigation of a pulmonary embolus, the aneurysm, of a sacciform shape, was located above the interline of the knee and often contained a thrombus: this site of onset facing the calf "venous pump" makes it an "experimental" emboligenic focus. The pulmonary embolus is a serious affection since it is repetitive: a pulmonary scan showed dissemination in the two fields of the hypovascularized zones. Identification of an acute or chronic cor pulmonale was a routine finding and a paradoxical embolus in the arterial territory was observed twice. Local surgery (venous repair or exclusion of the aneurysm) can be performed in association with anticoagulant therapy, but partial interruption of inferior vena cava appears to be the safer method of avoiding a recurrent embolus, which may be fatal.