Henties Bay Aerosol Observatory (HBAO)

The South East Atlantic offshore Southern Africa: a regional hotspot for aerosol-cloud-radiation interactions with global implications on climate

The interaction of clouds, aerosols and radiation is highlighted as key climate uncertainties in the recent Intergovernmental Panel on Climate Change (IPCC) assessment report (Boucher et al., 2013). Aerosol-radiation interactions stem from direct scattering and absorption of solar and terrestrial radiation by aerosols, thereby changing the planetary albedo. Aerosol-cloud interactions, also termed indirect effects, arise from aerosols acting as cloud condensation (CCN) in warm clouds. An increase in the number of CCN translates into larger concentrations of smaller cloud droplets, increasing cloud albedo. Both aerosol-radiation and aerosol-cloud interactions trigger fast adjustments to the profiles of temperature, moisture, and cloud water content, which ultimately affect cloud formation and precipitation rates (e.g., Johnson et al., 2004). The quantification of interactions in the cloud-aerosol-radiation system remains elusive. The recent IPCC report (Boucher et al., 2013) stresses that aerosol climate impacts remain the largest uncertainty in driving climate change, with a global mean effective forcing of -0.50±0.40Wm-2 for the aerosol-radiation-interaction and in the range 0 to -0.9W m-2 for the aerosol-cloud-interaction thereby counteracting a significant, but poorly constrained, fraction of greenhouse gas-induced global warming which is estimated as +2.8±0.3W m-2 (Myhre et al., 2013a).

Our ability to provide reliable regional climate projections is further reduced downwind source regions, where aerosol radiative forcings are an order of magnitude larger than their global mean values. This holds particularly true for the South East (SE) Atlantic Ocean offshore Southern Africa, pointed as a regional hot-spot by the latest model exercise of the Aerosol Comparisons between Observations and Models (AEROCOM) project (Myhre et al., 2013b).

 

 

------------------ News ------------------

Apr, 2019
Training at WMO GAWTEC 36 course

Andreas Namwoonde, PhD student at NWU and site manager of HBAO, has been invited to participate to the 36th GAWTEC Training Course in Germany.

Aug, 2018
Student exchange between NWU and LISA

Danitza Klopper, PhD student at NWU, has visited LISA for 3 months.

Dec, 2017
Sixth GDRI-ARSAIO meeting in Durban, South Africa

Scientists participating in the GDRI-ARSAIO (CNRS/NRF) gathered together in Durban for their sixth scientific meeting.

Aug, 2017
Namibia, here we come!

The Aerosol, Radiation and Clouds in southern Africa (AEROCLO-sA) field campaign will take place in Namibia from 23 Aug to 12 Sept 2017.

Sept, 2016
L’observatoire atmospherique HBAO en Namibie labellisé station regionale par l’OMM

La station de mesures atmosphériques Henties Bay Aerosol Observatory a reçu officiellement, le 16 juin 2016, le label Regional GAW de l’Organisation Météorologique Mondiale.

Dec, 2015
Fourth GDRI-ARSAIO meeting in Cape Town, South Africa

Scientists participating in the GDRI-ARSAIO (CNRS/NRF) gathered together in Cape Town for their fourth scientific meeting. Discussions and scientific presentations took place at the CSIR in Stellenbosch as well as at the GAW station at Cape Point. Next meeting will be held in La Reunion Island in December 2016.

Nov, 2015
Training session at LISA and LOA

Andreas Naamwonde and Mattheus Hanghome, observers at HBAO, have visited LISA and the Laboratoire d’Optique Atmospherique (LOA) in Lille to get advanced training on the scientific instrumentation operated at the station. In this framework, they also visited the PEGASUS mobile station involved in the AEROCLO-sA field campaign in Sept 2016, as well as the atmospheric simulation chamber CESAM.

Oct, 2015
First international SEALS-sA meeting in Windhoek, Namibia

The first international Sea Earth Atmosphere Linkages Study in Southern Africa (SEALS-sA) meeting has taken place at the Polytechnic of Namibia on the days of October 7-8, 2015. An international group of scientists and decision makers (including Namibia, Angola, Botswana, South Africa, France, United Kingdom and the United States of America) has come together to build an international science initiative to understand the interactions of the biosphere, atmosphere, land and ocean in the southern African subcontinent. Sixteen scientific presentations and an open discussion have taken place.

Oct, 2015
A new visit to HBAO

Regular maintenance is important to ensure the quality and traceability of the data. A new visit to HBAO has taken place at the beginning of October to verify the correct behavior of the instruments. Everything works well, apart from the PARTISOL sampler which is giving troubles. The sun as well… not shining!