April, 2017

Introduction


"Forests have low surface albedo and can mask the high albedo of snow, which contributes to planetary warming through increased solar heating of land." - Bonan, 2008

Goal and Objectives

Goal: use satellite imagery to further understand the causes and consequences of forest induced clouds.

Objectives were to;

  1. Automatically detect forest enhanced clouds

  2. Ascertain preferred weather conditions for forest induced clouds

  3. Determine effects of the additional clouds on the radiation balance

Study Area

Largest temperate forest without orographic effects of Europe

Satellite Data

Meteosat Second Generation

  • EUMETSAT
  • Meteorological satellite
  • Geostationary
  • Resolutions:
    • 15 min temporal
    • HRV channel: 400–1100 nm spectral
    • 1x1 km spatial
  • Data range
    • May – August of 2004 – 2013

1. Automated Detection - Method

Own Method

  • No training and ground measurements needed

1. Automated Detection - Results

  • Own Method worked poorly
    • < 30% of images correctly classified
  • Neural Network
    • Much training needed and even worse performance
  • Manual classification of 10.000 images

2. Weather Conditions - Method

  • Compare additional cloud formation conditions with average
  • Test for significant different mean
    • Temperature, pressure and wind speed
  • ERA Interim archive from ECMWF
    • 80x80 km spatial and 3 hour temporal resolution

2. Weather Conditions - Results


Additional clouds during warm and calm weather
      \(\rightarrow\) High-pressure area

3. Albedo Effect - Method

Comparing clear-sky with average reflected radiation

  • Difference forest ( – ) and non-forest ( – )

3. Albedo Effect - Results

  • Nearly no difference on average

3. Albedo Effect - Results

Current conceptual understanding (Bonan, 2008)

3. Albedo Effect - Results

Proposed conceptual model

Discussion & Recommendations

  • Prioritize improving automated detection
    • Allows studying of more images and other areas
    • Suggestions: pattern recognition, space-time, other MSG channels
  • Implement new concept in climate models

Conclusions

1.Automatically detect forest enhanced clouds

\(\rightarrow\) Requires more advanced method

2.Preferred weather conditions for forest induced clouds

\(\rightarrow\) Warm and calm weather: high-pressure area

3.Consequences for the radiation balance

\(\rightarrow\) Clouds compensate for lower forest albedo

Questions?



Supplement 1