Modland volumes and loads status
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MODLAND Volumes and Loads Status. MODIS Land Science Team Workshop July 15, 2003 Robert Wolfe MODIS Land Team Support Group NASA GSFC Code 922, Raytheon ITSS. Land Products @1x – EDC DAAC. 2/96 baseline was 154GB/day 10/99 baseline is 330GB/day (with combined Aqua/Terra products)

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MODLAND Volumes and Loads Status

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MODLAND Volumes and Loads Status

MODIS Land Science Team Workshop

July 15, 2003

Robert Wolfe

MODIS Land Team Support GroupNASA GSFC Code 922, Raytheon ITSS


Land Products @1x – EDC DAAC

  • 2/96 baseline was 154GB/day

  • 10/99 baseline is 330GB/day (with combined Aqua/Terra products)

  • Current Collection 4 reprocessing volume is 310GB/day (no combined products)

  • Land volume will be 240GB/day in Collection 5 reprocessing (reduced L2G volume and other changes) in Fall 2004


Land Products @1X – NSIDC DAAC

  • 2/96 baseline was 13GB/day

  • 10/99 baseline is 40GB/day

  • Current Collection 4 reprocessing volume is 15GB/day

  • Snow and Sea Ice product volume will be 25GB/day with Collection 5 reprocessing in Fall 2004


Proposed C5 Volume Changes

  • Objective to estimate:

    • how to further reduce the size of the L2G products, and

    • start generating 500m data for a number of products that are currently only produced at 1km

  • Changes implemented for a Collection Version 5 reprocessing

    • likely to begin next fall

    • will mean changes for downstream software

  • Compression could also help with throughput

    • will be considered separately

  • Did not consider:

    • changing the compositing period for 8-day products

    • eliminating any products (except when replaced by 500m products)

    • any Land products archived at NSIDC (only EDC products)


L2G Option A

  • Reduce the number of L2G products archived from 7 to 2 per tile

    • incorporate the pointer and geoangle products into the surface reflectance products

  • Savings from:

    • removing the "orb_cov" field

    • eliminating the "line" and "sample" fields

    • removing overlap between scans

  • Impact: reduces the L2G products to less than half the current size

    • From 251 GB/day to 120 GB/day

    • But … MOD09HK is now a more complicated product because it has both a 1km and 500m grid within the same file


L2G Option B

  • Turn the L2G product into a "AGG" product

    • eliminate the need to have both a daily L2G surface reflectance and a daily Aggregated surface reflectance

  • Same criteria for selecting observations as in the current MODAGG code will be used

    • maximal angular distribution of the good observations; no more than 4 orbits/day

  • Non-compact (full) form is used

    • each layer is stored as a single 2-dimensional array

    • savings from reducing the need for storing the links between the different resolutions

    • additional space is needed to go to the non-compact form, and to add the texture field

  • Impact: the L2G products to about 2/3 of current size

    • From 251 GB/day to 165 GB/day (vs. 120 GB/day for Option A)


Generating four current 1km products at 500m

  • Candidate 1km products: BRDF/Albedo, LAI/FPAR, PSN/NPP and Land Cover

  • Need an intermediate AGG/TEX at 500m or L2G option B

  • Current candidate 1km product size: 6.5 GB/day

    • excludes 1km AGG/TEX (current size 51.4 GB/day, reduced volume: 25.7 GB/day)

  • Estimated new 500m product size: 17.8 GB/day

    • excludes 500m AGG/TEX (reduced volume: 102.7 GB/day)

  • Easily fits with L2G Option B or for L2G Option A if AGG/TEX is not archived


Summary


Volume Drivers

  • Main drivers

    • Extending Terra and Aqua mission lifetimes three years (from 5 to 8+ years)

    • Volume growth from ’96 baseline

    • Archive management issues

      • Previous collection must be kept for 6 months after current one – tape reuse is more difficult than anticipated

  • Solution: Technology refresh

    • Anticipated for about this time

    • New drives write 3 times as much data on tapes, current tapes are being reused


Strawman MODLAD Volume Recommendations

  • Reduce size of L2G products using Option A or B and start producing new 500m products (reduces volume by ≥ 27%)

  • Implement internal HDF compression where feasible

    • Must consider any impact on end-user analysis tools

  • Perform technology upgrades to keep tape archive current

  • Plan for C5 reprocessing at 5.6X (means reprocessing time is about 1 year) – by reducing overall size (including oceans) the bottleneck will be Level 1 processing

  • Increase size of data-pools and tie data-pools to ordering interface (so data in pool doesn’t need to be staged from tape)

  • Work with land community to better understand product usefulness


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