WMO WWRP e-Newsletter | No.5 | January 2018

Can the assimilation of atmospheric constituents improve the weather forecast?

          The atmosphere contains many gases that influence both the weather and the climate even if they are present in small amounts. One noticeable example is their ability to warm or cool different parts of the atmosphere through their radiative effects. These radiative effects are the main reason why atmospheric constituents are included in Numerical Weather Prediction (NWP) models.
          There is another interesting property of some of these constituents that is not yet fully explored: they are skillful tracers of the atmospheric flow. Therefore, assimilating observations related to these constituents could in theory provide information on the atmospheric dynamics. This was demonstrated by Daley (1995) with a one-dimensional constituent transport equation and a prognostic linear wind model. The first successful application of this idea to NWP is from Semane et al. (2009). They assimilated ozone profiles from the Microwave Limb Sounder (MLS) experiments in Meteo-France global NWP model using a four dimensional variational (4D-Var) assimilation technic. They demonstrated a subsequent reduction of the wind bias in the lower stratosphere.
          Since then, both the models and the quality of the atmospheric constituents measurements have improved. The number of observations also notably increased and more and more atmospheric constituents are observed. In particular, the Infrared Atmospheric Sounding Interferometer (IASI) provides retrieved products of carbon dioxide (CO2) and methane (CH4) with a dense global coverage and a low bias (Crevoisier et al., 2013). In order to revisit the possible impact of assimilating atmospheric constituents on weather forecasts, we have assimilated the CO2 and CH4 IASI retrieved products using an ensemble Kalman Filter (EnKF), which is available in research mode at the European Centre for Medium-Range Weather Forecasts (ECMWF, Hamrud et al., 2015).
          This choice of assimilation method makes our approach complementary to the one of Semane et al. (2009). By design, the EnKF provides cross-correlations between the forecast errors of the atmospheric constituents and the meteorological parameters. These cross-correlations propagate any information on atmospheric constituents to the meteorological parameters (and vice versa). Over a period of two months of the winter 2010 we ran two experiments: one with and one without the assimilation of the CO2 and CH4 IASI products. From the comparison between the two experiments, we found that the assimilation of atmospheric constituents has a significant positive impact on wind forecasts in the mid-stratosphere of the summer hemisphere for all forecast range from 12 hours to 10 days and a slightly negative but not significant impact in the troposphere (see Figure). The forecasts of other meteorological parameters like temperature are affected too, but the impact, still positive in the mid-stratosphere, is significant for a shorter forecast range (up to 5 days).
          Figure 1: Change in root mean square error (RMSE, solid line) and associated error (shade) in % between an experiment assimilating CO2 and CH4 and an experiment without, for the southern hemisphere: (a) vertical profile for the wind error reduction for the forecast at day 4, (b) time series of the wind error reduction at 20hPa, (c) same as (b) but for the temperature. A negative value means that the RMSE of the CO2 and CH4 experiment is lower than the one from the reference experiment (better) when verified against ECMWF operational analysis. The improvement (degradation) is significant if the shaded area is below (above) the zero line. Statistics obtained for the period of January & February 2010.
         Overall this work proves that the assimilation of atmospheric constituents can have a positive impact on NWP forecasts when accounting for the cross-correlations between the forecast errors of the atmospheric constituents and the meteorological parameters. The next steps are the assessment of the impact of the join assimilation of atmospheric constituents and weather-related measurements when using a variational assimilation method like the one used by Semane et al. (2009) or the one used operationally at ECMWF.

Article contributed by Sebastien Massert (ECMWF)

Featured Expert:  Frederic Vitart

          Frederic Vitart  has an extensive scientific research background in weather and climate.  A leading scientist in the field of seasonal and monthly forecasting he has over 20 years of expertise in operational probabilistic forecasting  and numerical model development at the European Centre for Medium Range Weather Forecasting (ECMWF). He is known widely for the implementation of a 30-day weather forecasting system and evaluation of the predictability at the sub-seasonal time scale. He had also worked on subseasonal to seasonal prediction of tropical storm activity in coupled ocean-atmosphere general circulation models. Other professional interests of Frederic includes Madden-Julian Oscillation (MJO), Tropical-extratropical interactions and Forecast verification. He started his professional career as a visiting scientist at the Los Alamos National laboratory, from November 1990 to February 1992, where he worked on implementing numerical algorithms on a massively parallel supercomputer. That same year he went back to France and was appointed Research Scientist at the Commissariat a l'Energie Atomique (CEA). Shortly after gaining a PhD degree on Ocean and Atmospheric Sciences from Princeton University in 1998, he joined ECMWF as a research scientist. He now leads the centre's research on extended-range forecasting. For eight years, Frederic was the Chair of WWRP's Expert Team on Seasonal Tropical Cyclone Forecasting. He is a former member of WMO's WGNE/MJO Task Force and is currently the co-chair of WWRP's Sub-Seasonal to Seasonal Prediction Project (S2S). 

IWM-6: The Global Monsoon System: Research and Forecast of Severe Monsoon Weather and Climate Impacts

          The sixth International Workshop on Monsoons (IWM-6) took place in Singapore from 13 to 17 November 2017. The event was hosted by the Government of Singapore and organized by the WWRP/WGTMR Monsoon Panel chaired by Professor Chih-Pei Chang. Co-sponsors of the workshop included several groups across WWRP and WCRP, including the MJO Task Force, the GEWEX/CLIVAR Monsoon Panel, the S2S Steering Group, and the Years of Maritime Continent (YMC) Scientific Steering Committee. The workshop provided a forum for researchers and forecasters to discuss recent advances and current issues covering all time scales (meso-, synoptic, extended range, intra-seasonal, climate) that are relevant to the forecasts of high-impact weather in the monsoon regions around the world. It was also an effective means to transfer new science and technology to National Meteorological and Hydrological Services in said regions since an established part of the IWM-6 is a training workshop that offers short courses to early career monsoon forecasters. Led by world-renowned experts in the field of monsoon study, close to 150 researchers and forecasters participated in the five-day workshop which opened with a special lecture dedicated to Dr Dev Raj Sikka, the recognized monsoon guru and polymath, who passed away on 18 March 2017.   As in previous IWMs, the sixth in the workshop series also included contributed papers in oral and poster forms. Highlight of the workshop are the invited reviews which will be finalized by the authors after the workshop and peer reviews, and will be published in a WMO-sponsored book: The Global Monsoon System: Research and Forecast, 4th edition.  During the workshop, Professor Chang received from WMO's Research Department, a Certificate of Appreciation  in recognition of his tireless service and meritorious dedication during the 10 years he served as Chairperson of the Monsoon Panel.


IWTCLP-4: Tropical Cyclone Landfall Impacts: Transitioning from Observations and Modeling to Greater Understanding and Better Forecasts

          The Fourth International Workshop on Tropical Cyclone Landfall Processes (IWTCLP-4) was held in Macau, China from 5 to 7 December 2017. The workshop was organized by WWRP's Expert Team on Tropical Cyclone Landfall Processes in partnership with WMO's Tropical Cyclone Programme. Chaired by Dr Robert Rogers, the workshop provided a forum for discussion between researchers and forecasters on the current status of tropical cyclone landfall processes and on priorities and opportunities for research. More than 60 leading research scientists and warning specialists working on topics related to tropical cyclone landfall examined current knowledge, forecasting and research trends from an integrated global perspective. The workshop offered a number of recommendations for future forecasting studies and research with special regard to the varying needs of different tropical cyclone affected regions. The recommendations emanating from the workshop will be presented at the upcoming Ninth International Workshop on Tropical Cyclones (IWTC-9) (Hawaii, USA, 3-7 December 2018). IWTCLP-4 was followed by a Progress Meeting of three TCP/WWRP Tropical Cyclone related Forecast Demonstration and Research Projects.

Article contributed by Robert Rogers (NOAA)

R/V MIRAI's  Years of the Maritime Continent Cruise 

          The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) organized a send-off ceremony for the Japanese Oceanographic Research Vessel (R/V) MIRAI on its Years of the Maritime Continent Cruise. The event was held on 19 November 2017 at the Singapore Cruise Center. The participants were welcomed on board by Dr Satoru Yokoi, Chief Scientist of the YMC Cruise. Dr Yoshihisa Shirayama, Executive Director of JAMSTEC delivered the opening address during the ceremony. Representing WMO at the event was Dr Deon Terblance, Director of WMO's Research Department. Included in the commemorative event was a special open house program for participants. Converted from a former nuclear powered ship (MUTSU) R/V MIRAI is one of the largest class of research vessels in the world able to perform observational studies over wide areas under rough weather conditions. Equipped with large observation instruments, a Doppler radar, MIRAI is able to carry large observation instruments, including 14 large-scale buoys (TRITON buoys), as well as large water samplers and piston corers. The vessel even has the ability to conduct research in severe ocean conditions such as Arctic Ocean as it is equipped with a hybrid type anti-rolling system and featuring an ice-resistant structure. MIRAI is joining the intensive observations around the Sumatra Island in Indonesia from November 2017 to January 2018 as part of the project “Years of the Maritime Continent (YMC)”. The goal is to better understand the variability of the weather-climate system, and to contribute to improving prediction skills, over the “Maritime Continent” – the Earth's largest archipelago bridging the equatorial Indian and Pacific Oceans.

Article contributed by Kunio Yoneyama (JAMSTEC)

AvRDP at the AMSC2017

          The 2017 Aeronautical Meteorology Scientific Conference (AMSC-2017) hosted by Meteo-France was held in Toulouse from 6 to 10 November 2017. The theme of the conference is: Aviation, Weather and Climate: Scientific research and development for future aeronautical meteorological services in a changing atmospheric environment. The objective of the event is to provide an overview of the current state-of-the-art and foreseen advances in meteorological science and technology needed to underpin the changing global aviation industry. In 2015, WMO's 17th Congress (Cg-17) established the WWRP Aviation Research Demonstration project (AvRDP) and endorsed the engagement of WMO, in close collaboration with the International Civil Aviation Organization (ICAO), in supporting the meteorological components of ICAO’s Global Air Navigation Plan (GANP) and Aviation System Block Upgrades (ASBU)  methodology. A year later, the 68th Session of WMO's Executive Council (EC-68) agreed with the general principles for extended research activities on aviation, building on the progress of the current AvRDP and taking into consideration the envisaged performance improvements in the ASBU with focus on transfer of the research results into operational practice.  EC-68 also endorsed the organization of the AMSC in 2017 with broad participation of research, operation and user communities and with the objective to identify needs and plan the research activities in line with the ICAO's GANP and its ASBU methodology. The unique event is expected to stimulate special research focused on high impact weather affecting safety and efficiency of aviation, foster rapid transition from research to operations and ease in the transition of the AvRDP into an Inter-commission (CAS/CAeM/CBS) project. In addition, the event also raised awareness of the potential impacts of climate change and variability on aviation operations now and into the future.  

Article contributed by Peter Li (HKO)

S2S Phase 1 Report to be published soon

          The Subseasonal to Seasonal Project (S2S) Phase 1 report describes the project’s progress and main achievements from its inception in 2013 up to July 2017 and outlines some outstanding challenges. All the main activities foreseen in the S2S implementation plan have been carried out to some degree. The signature achievement of S2S has been the creation of the S2S database of sub-seasonal forecasts (available to the research community three weeks behind real time) and re-forecasts, archived at the European Centre for Medium-Range Weather Forecasts (ECMWF) and the China Meteorological Administration (CMA). Launched publicly in May 2015, the S2S database has inspired a major research activity on S2S predictability, modeling, and forecast verification and product development. The project has fostered S2S research by organizing/co-organizing 18 science workshops/sessions in the project’s first four years, together with eight training courses. Six S2S sub-projects were established as a means to coordinate research and to develop the global S2S climate and weather research community.  To date, 23 articles that used the S2S database have been published in peer-reviewed literature. Several of the findings relate to the Madden-Julian Oscillation (MJO). Effective coordination among operational centres facilitated by S2S encouraged the WMO Lead Center for Long-range Forecasts in 2015 to begin a pilot real-time sub-seasonal Multi-model Ensemble (MME) prediction system for its members, taking advantage of the S2S database at ECMWF.  Further, coordination across the WMO Global Producing Centres of Long-Range Forecasts (GPCLRFs) has taken place such that all of 11 operational centres now issue forecasts on Thursdays (including the 4 models with daily forecast starts) as compared with only 7 of 11 models at the project’s outset. This greatly facilitates the generation of multi-model ensemble forecasts. While the mid-term report can point to major achievements and project successes, there is a clear recognition that much of the research, product development and uptake by the applications communities are still at quite early stages.  Much remains to be done to fully realize the S2S vision of seamless forecasting both in terms of improving the skill of the forecasts, developing the operational infrastructure, as well as creating forecast products to help inform user-decisions in the two-weeks-to-two-months range. A focus on a combination of such upstream and downstream issues is foreseen in the second phase of the project.
          Key personalities in the field of data assimilation including a significant number of early career scientists gathered in Florianopolis, Brazil from 11 to 15 September 2017 for the Seventh International WMO Symposium on Data Assimilation (WMO DAS 2017). Hosted by Brazil's Centro de Previsao de Tempo e Estudos Climaticos (CPTEC/INPE), the symposium was organized to address the challenges and trigger innovations on advanced data assimilation methods for a wide spectrum of applications in atmospheric, oceanic and earth system science. Presentations at the event represented the most innovative ideas and developments in data assimilation. The WMO DAS 2017 encouraged the participation of early career scientists and promoted equal opportunities not only to them but also to scientists from developing countries by allotting equal presentation time to all oral presenters.  Data assimilation themes at the Symposium included advancing assimilation methodologies and ensemble data assimilation methods; assessment of model and assimilation system uncertainties; data assimilation performance assessment and diagnostic tools used; coupled state (atmosphere/ocean, tmosphere/land, atmosphere/cryosphere) data assimilation methodology; polar and tropical data assimilation issues and solvers; impact assessment of the observations used and observations needed in the future; representation of high-impact weather phenomena from tropical cyclones to urban smog; convective scale data assimilation methodology and observations; assimilation of different atmospheric constituents.The Symposium had 75 20-minute talks and 150 posters that represent the state of the art in data assimilation methodologies and applications. A plenary session was organized on the last day of WMO DAS 2017 to provide a summary of the main achievements in the field of data assimilation and gather from participants recommendations for further investigations and opportunities for improvements.

Science Summit on Seamless Research for Weather, Climate, Water and Environment

          The Science Summit, organized by the WMO Commission for Atmospheric Sciences (CAS) took place in Geneva from 20 to 22 October 2017. Unlike previous technical conferences that preceded CAS sessions, the summit which came before the 17th session of the Commission for Atmospheric Sciences (CAS-17) followed a novel approach. The Science Summit in 2017 had three major components each of which was equally important to achieve the aims of the event. It's main aims were to provide an opportunity for a forward-looking debate on some of the solutions related to the primary scientific and research challenges that WMO Members are facing; to foster a common understanding between operations and research community and other international research initiatives on a new model of co-design to optimize research and innovation as well as operations interplay in the interest of users; to build a strong unified vision on those research topics central to dramatic advances in predictive skill across time scales for weather, climate, water and related environmental issues and to give clear recommendations to WMO Members through the Executive Council and Congress on research and innovation priorities, how these will benefit the world and how best these should be resourced. The discussions at the Science Summit revolved around the topics covered in the  documents prepared for CAS-17 and was structured in five thematic sessions. For each of these sessions, a set of key questions had been developed, which helped to steer and target the discussions. The ideas and suggestions that were developed during the Science Summit was directly fed into CAS-17 and guided the decisions and recommendations made by the Commission. The Summit was also focused on closing the gap between research and the derived societal benefits. Key-note speakers included renowned scientists from different fields of atmospheric and related sciences and a broad range of institutions.  In addition to the presentations and discussions, a poster session was organized to allow for further scientific exchange among the participants. 

HIWeather: Conference on Predictability and Multi-scale Prediction of High Impact Weather

          WWRP's High Impact Weather Project (HIWeather) in partnership with the Waves to Weather Research Center co-sponsored the Conference on Predictability and Multi-Scale Prediction of High Impact Weather in Landshut, Germany from 9 to 12 October 2017. The Conference aimed to advance progress in the prediction of high impact weather by bringing together the academic and operational research communities. Participation at the conference was limited to about 100 attendees to provide ample opportunities for discussion and networking. The conference programme featured discussions on fundamental challenges in the prediction of high impact weather and keynote presentations on the following topic areas: the role of scale interactions and error growth in limiting the predictability of high impact weather; impact of diabatic processes on predictability of high impact weatjher, multi-scale prediction systems, including data assimilation strategies for high impact weather prediction; probabilistic forecasting, incéuding statistical post-processing methods; evaluation and improved modeling of cloud and planetary boundary layer processes; prediction of high impact weather in urban areas; integrated environmental prediction; extreme weather events such as floods, damaging winds and heat waves. The papers and discussion were of very high standard and presented well the crucial scientific activity taking place to understand and predict hazardous weather events. Two highlights of the event were a joint discussion with WMO's Global Atmospheric Watch Urban Research Meteorology and Environment (GURME) scientists on prospects for urban weather prediction, and discussion of possibilities for wider involvement of HIWeather in the 2018 Remote sensing of Electrification, Lightning And Meso-scale/micro-scale Processes with Adaptive Ground Observations (RELAMPAGO) experiment in Argentina.
Article contributed by Brian Golding (UKMO)

First Special Observing Period for Year of Polar Prediction 

          The Year of Polar Prediction (YOPP) is one of the key elements of WWRP's Polar Prediction Project (PPP). YOPP's mission is to enable a significant improvement in environmental prediction capabilities for the polar regions and beyond, by coordinating a period of intensive observing, modelling, verification, user-engagement and education activities. YOPP will be implemented in three different stages: a preparation phase (2013-2017), a YOPP core phase (mid-2017 - mid-2019), and a consolidation phase (2019-2022). The core phase of YOPP will entail intensive observations and modelling campaigns in both the Arctic and Antarctic scheduled from mid-2017 to mid-2019.  Three Special Observing Periods (SOPs) are planned during the YOPP core phase. The first SOP will be in the Arctic to commence on 1 February until 31 Mar 2018.  The second SOP also in the Arctic is scheduled from 1 July to 30 Sep 2018 and the third SOP, this time in the Antarctic, is planned from 16 November 2018 to 15 February 2019. These SOPs are dedicated to enhance routine measurements and investigations of physical phenomena, the development and improvement of numerical forecasting models, and the verification and improvement of forecasting services.

WWRP Event Calender Jan-Apr 2018

PPP 13-15 March 2018 Reykjavik, Iceland
The Ninth Polar Prediction Project Steering Group meeting

S2S 8-13 April 2018 Vienna, Austria
European Geosciences Union Session  on S2S

PPP 16-22 April Wageningen, Netherlands
Fourth Session PPP-SERA Meeting 

PPP 17-27 April 2018 Abisko, Sweden
Second Polar Prediction School 


Editorial Board

Celeste SAULO (CIMA)
Jian Jie WANG (CMA)

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Editorial Assistant.   Juhyeong HAN
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