In diesem Vortrag werden Ergebnisse aus den Projekten ACACIA und BeCoM gezeigt. Die Arbeiten hatten und haben zum Ziel, die Vorhersage persistenter Kondensstreifen verläßlicher zu machen

Gierens, Klaus Martin

Hofer, Sina Maria

Sperber, Dario

Institute of Transport Research:Publications

Forecasting ice supersaturation and persistent contrailsKlaus Gierens, Sina Hofer, Dario Sperber Institut für Physik der Atmosphäre, DLR, OberpfaffenhofenGreener by Design Conference 202321 October 2023 Grant No. 101056885ACACIAGrant No. 875036Forecast of persistent contrails and their individual climate effect2 27.09.2023Necessary steps for avoiding contrails:1. Predict the formation of contrails with a reasonable skill Schmidt-Appleman criterion2. Predict the formation of persistentcontrails with a skill that is sufficient for deviating air traffic Predict the occurrence of ice super-saturated regions (ISSRs )3. Predict the RF (ERF, ATR, ...) associated with individual contrails with a skill that is sufficient for deviating air trafficWilhelm et al., 2021How well can persistent contrails be predicted?Gierens, Matthes and Rohs, 2020: Analysis of 4 months of IAGOS data3 27.09.2023Schmidt-Appleman criterion (RHmax>1) Contrail persistence criterion (RHi>1)ETS=0.76 ETS=0.08Part 1: Test of dynamical proxies4 27.09.2023Conditional distributions of RHi5 27.09.2023Red: No contrails or at least no persistence possible (acc. to IAGOS data)Black: Persistent contrails possible (acc. to IAGOS data)Blue: Persistent contrails with strong instantaneous RF possible (acc. to IAGOS)Wilhelm, Gierens, and Rohs, 2021: Analysis of 10 years of IAGOS dataMany quite dry cases in ERA-5 where IAGOS measurements show ice supersaturation and SAC fulfilled Dynamical proxies: Relation between ISS and PV, , , ZDistinct conditional distributions6 27.09.2023PV  Zred: ISS, blue: no ISS06.06.2022Use dynamical proxies in a Bayesianlearning procedure:log Ω 𝑥 = logΛ+ logΠwithΩ 𝑥 = 𝑃 𝐼𝑆𝑆|𝑥 /𝑃 𝐼𝑆𝑆|𝑥Λ = 𝑓𝑋 𝑥|𝐼𝑆𝑆 /𝑓𝑋(𝑥|𝐼𝑆𝑆)Π = 𝑃(𝐼𝑆𝑆)/𝑃(𝐼𝑆𝑆), logΠ ≈ −2Unfortunately too small log-likelihood ratios (almost always < 2). Thus the probability for ISS does hardly raise above 1/2.Log-likelihood ratios are too small!7RHi(ERA5)06.06.2022GAM:     log Ω|𝑥 = 𝛽0 + σ𝑓𝑖(𝑋𝑖)• inclusion of RHi(ERA5) is essential• ETS values do not get larger than about 0.38• inclusion of proxies does not raise ETS significantly• a priori correction of  RHi does not help• better results are prohibited by the large overlap btw. the cond. pdfsRegression using generalised additive models (GAMs)8overlap06.06.2022Reducing the overlap of the conditionalpdfs raises the ETS of the GAM substantially.This points to the problem that needs tobe overcome in NWP.Test of the GAM with artificial pdfs (RHi) with reduced overlap9original:ETS=0.372slight shift:ETS=0.765stronger shift:ETS=0.956Hofer et al., in prep.Part 2: New concept of a one-moment ice cloud scheme for NWP models10 27.09.2023New One-Moment Scheme avoiding saturation adjustment • New scheme assumes sub-grid variability in the humidity field• Whenever the humidity threshold for homogeneous nucleation is passed locally within a grid box, the resulting cloud fraction is predicted• Exponential decay of specific humidity assumed in the cloudy part of the grid box instead of instantaneous conversion of all supersaturation to ice (saturation adjustment)11 27.09.2023Sperber and Gierens, 2023, in pressNew One-Moment Scheme avoiding saturation adjustment  Considerably larger supersaturation during cloud formation, but also in the agedcirrus cloud.12 27.09.2023Grid mean relative humidity In-cloud mean relative humiditySummary and further research Aviation contributes to climate change (warming) through CO2 emission and non-CO2 effects. The latter are short-lived and strongly situation-dependent. This implies that they can be lowered by a climate-aware flight-planning. Strongly warming persistent contrails can be avoided if flights avoid ice supersaturated regions. The forecast of the latter is challenging. We need improved representations of ice-clouds and their supersaturated environment in NWP models. We need many more good humidity measurements at cruise level for data assimilation. We need better detection of contrails in satellite data for validation.13 27.09.2023

Forecasting ice supersaturation and persistent contrails

https://elib.dlr.de/199592/1/Gierens-GbD-2023.pdf

Forecasting ice supersaturation and persistent contrails

Abstract

Similar works

Full text

Available Versions

Institute of Transport Research:Publications