A document by Alexis Mariaccia. Click on the document to view its contents.

We have conducted an investigation into the coupling between the stratosphere and troposphere, focusing on perturbed and unperturbed scenarios of the northern hemisphere polar vortex. These scenarios were established in a previous study, which categorized the main winter typologies based on the timing of sudden stratospheric warmings (SSWs) and final stratospheric warmings (FSWs). Here, we further analyze the mass-weighted divergence of the Eliassen-Palm (EP) flux to confirm the association between these scenarios and the specific timing of momentum and heat flux deposition by planetary waves. Our analysis reveals that wave-1 and wave-2 contributions to this divergence confirm distinct wave activity effects in relation to these scenarios. Additionally, examining the evolutions of the Northern Annular Mode (NAM) provides further insight, demonstrating that these scenarios represent unique states of both the stratosphere and troposphere, which mutually influence each other during the winter months. Of particular interest is the observation of descending stratospheric anomalies into the troposphere following SSWs, often accompanied by a negative phase of the Arctic Oscillation (AO). Notably, we have made an important discovery regarding surface precursors for perturbed scenarios in early winter, specifically December. These surface precursors display wave-like patterns that align with the diagnosed wave activity in the upper stratosphere. This finding establishes a connection between early and late winter, highlighting the importance of these precursors. Consequently, our results enhance our ability to anticipate the behavior of the polar vortex and its impacts, thus holding significant implications for sub-seasonal to seasonal forecasts in the northern hemisphere.

Monitoring Earth Energy Imbalance (EEI) is absolutely fundamental to understand and prevent climate change as it corresponds to the Earth’s excess heat. In particular, measuring radiative forcing in an environment with a wide range of conditions entails a better understanding of its impact on the climate.The UltraViolet and infrared Sensors at high Quantum efficiency on-board a small SATellite (UVSQ-SAT) aims to improve measurements of those radiations at Top Of the Atmosphere (TOA). It becomes a pathfinder for Radiation Budget measurements on-board a CubeSat demonstrating a disruptive technology, implementing miniaturized sensors on a small satellite (twelve miniaturized thermopiles sensors and four photodiodes). This project is promoted by the University of Saint-Quentin-en-Yvelines with the support of the International Satellite Program in Research and Education (INSPIRE). The satellite will be launched and in-orbit in December 2020.One of the main purposes of the mission is to measure the Essential Climate Variables (ECV) more precisely using multi-point observation, in an effort to improve spatiotemporal coverage through future constellation. The scientific goals of the mission are first to observe incoming solar radiation and outgoing terrestrial radiations at Top Of the Atmosphere. The second purpose is to measure solar spectral irradiance in the Herzberg continuum. Finally, the third objective is to improve the technological readiness of a sensor.This session will focus on the ability to define the spatiotemporal accuracy required to monitor the variability of those Essential Climate Variables. Therefore, it will allow us to determine the number of satellites and characteristics of the future constellation meeting these specifications.