SGP/VISST/X1 - Algorithm version 4.1 instead of 4.0

During the original processing in 2012, 5 days 2012-02-17/21 were missing because of 
missing model input data. In 2015, the data for the entire month were reprocessed using an 
alternate source for the model profiles to fill in this gap.
The VISST process in use in 2015 is a slightly improved version 4.1 compared to the 
original v. 4.0.
Improvements include:
1) Updated cloud mask to improve low cloud detection in twilight
2) Reduced false cloud detection over desert and ocean
3) Improvements in multi-layer cloud detection (such as classifying deep convective clouds 
as single layer clouds)
4) For GOES-xx satellites: for GOES-12 onwards, 12um channel is missing. In V4.1 a 2 
channel algorithm using only 11 & 3.9um channels is used at night.

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• cloud top pressure(cloud_top_pressure)
• Split-Window Channel temperature (11.9 um)(temperature_sw)
• cloud optical depth(visible_optical_depth)
• Visible reflectance (0.65 um)(reflectance_vis)
• IR cloud emittance(ir_cloud_emittance)
• cloud effective height(cloud_effective_height)
• Broadband longwave flux average(broadband_longwave_flux)
• Infrared Channel temperature (10.8 um)(temperature_ir)
• cloud bottom height(cloud_bottom_height)
• Effective cloud temperature(cloud_effective_temperature)
• Effective cloud pressure(cloud_effective_pressure)
• cloud phase(cloud_phase)
• Altitude of cloud top used in retrieval(cloud_top_height)
• Near Infrared reflectance (1.6 um)(reflectance_nir)
• Particle size average(particle_size)
• Liquid or Ice Water Path(liquid_water_path)
• cloud bottom pressure(cloud_bottom_pressure)
• Solar Infrared temperature (3.9 um)(temperature_sir)
• broadband SW albedo(broadband_shortwave_albedo)