1. Climate change and Variability-Issues for ATM
Dr. Herbert Puempel,
WMO Commission for Aeronautical Meteorology
Co-Chair, ET-Aviation, Science and Climate

2. Observed changes:
Changed flow pattern at altitude: poleward shift of jets, High- Amplitude-Low wavenumber regimes, more turbulence
Sea level rise – Risk for coastal, low lying aerodromes
Increase of storminess: RWY in use restricted reducing capacity, increased risks, more turn-arounds, balked landings
Changes to typical convective scenarios: Higher CB-tops, quasi- stationary or slow-moving convective storms > aerodrome shut-downs
High Ice Content at altitude
Prolonged heat waves > reduced range/payload, air quality issues

3. Model projections
Highly regionalized changes: Russian Federation study shows large differences in temperature changes per region, Alps, Arctic strongly affected
Likelihood of “early occurrence of long term projections”: Projected “new normal” state for 2100 may occur temporarily and regionally any time soon
Understanding of Derived parameters emerging, but larger uncertainty:
Application of algorithms to climate model projections e.g. shows strong increase of turbulence, thus
need for scenario-based validation

4. Increased risk from crosswinds
Higher surface wind speeds in ”ex-hurricanes” crossing Europe (first observed in 1987 in UK)
Stronger meridional flows as a result of High Amplitude – Low Wavenumber regimes
Regulatory issue of calculating crosswinds (only gust strength reported, not direction!)
(e.g. 60kt winds @ 30deg from RWY orientation could be anything between 0 and 52kt crosswind component!)

5. convection and blocking of airways, STARs
Early indications of deeper convection > blocking of more levels
In low wind shear, extrapolation methods in forecasting difficult
No clear signal yet WRT hail, lightning, medium term increase likely
More perceptible water leading to higher risk of aquaplaning, RWY excursion
Lightning increase > longer shut-down for airports

6. turbulence and questions of RVSM
Application of turbulence algorithms to climate model runs indicates increase of mod/sev turbulence aloft (North Atlantic, P. Williams, Univ. Reading)
Requires confirmation by downscaling and observational evidence
Higher wind speeds in mid-latitude storms > higher risk of turbulence near CB, mountain waves, jets/fronts
Airways capacity issue if turbulence requires suspension of RVSM

7. RWY choice and cross-winds
Cold and shoulder seasons: higher incidence of storms with extreme surface wind speeds (”Ex-Hurricanes”)
No clear general trend WRT microbursts ( more “tropical” conditions in mid- latitudes, but regionally risk of tornadic storms may increase
Cross-winds in NH Mid-latitudes may increase due to stronger meridional flow (“High Amplitude – Low Wavenumber”)
Combination of cross-winds and RWY flooding in protracted convective events

8. In a Nutshell
Climate change is impacting aviation: - different weather phenomena (wind, convective scenarios, storms etc.) - changes are varying on regional level - the predictability of some weather phenomena is decreasing
Further work has to be done to better understand the ongoing changes combining meteorological science and operational expertise

9. Thanks to You for listening and showing interest
staff and leadership of Eurocontrol, Austrocontrol Airbus, NCAR, WMO and many other colleagues
or Figures, personal communications, feedback and encouragement