Currently Skimming:
3 Review of Individual Chapters
3 Review of Individual Chapters
Pages 14-32
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From page 14... ...
The committee suggests deleting "global" wherever it appears in this context. Specific remarks: L61-63: Wording implies that sea surface temperature variations are independent of anthropogenic forcing.
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From page 15... ...
Specific remarks: L 131, 138: "climate" should be replaced with "weather and climate" L225: "for" should be replaced with "with" L226: Delete "up through" L229: "supercede" should be replaced with "supersede" EXECUTIVE SUMMARY General remarks: Most of the key findings on attribution listed on P18-21 regarding surface temperature and rainfall trends are based on surface observations and climate model simulations, and thus can be assessed without reanalysis directly. The committee finds that most of the conclusions appear to be independent of reanalysis and that the authors need to strengthen the case that reanalysis is in fact critical in reaching these conclusions, for example by stressing the indirect use of reanalysis for the attribution of climate variability and in testing the Global Circulation Models (GCMs)
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From page 16... ...
It is becoming increasingly apparent that reanalysis should also include reanalysis of the chemical state of the atmosphere. There is great need for a skillful reanalysis using a global air quality model, for various reasons: understanding of aerosol-climate interactions, understanding of global transport of air pollution, provision of boundary conditions for regional photochemical simulations, etc.
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From page 17... ...
L609-610: "one measure of uncertainty" should be replaced with "a measure of part of the uncertainty" L610: "phenomena" should be replaced with "identifying phenomena" CHAPTER 2 REANALYSIS OF HISTORICAL CLIMATE DATA FOR KEY ATMOSPHERIC FEATURES General remarks: The committee feels that the chapter contains much useful material that serves to fulfill the mandates of the prospectus. It also feels that the chapter can be improved in several respects.
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From page 18... ...
, to be the main tool for quantifying decadal and long-term climate changes. The authors should also emphasize that reanalysis data will continue to be used largely for studying atmospheric processes and synoptic to interannual variations.
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From page 19... ...
For these reasons, model biases should perhaps be given a paragraph in this chapter, where they would be defined and briefly discussed, or this could be included in a text box. The committee finds that the report is relatively silent on the developing coupled data assimilation CFS reanalysis reforecast project.
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From page 20... ...
"Initial atmospheric conditions" were introduced in ~1970s, but what were the numerical weather predictions systems using before that? Also, the "detailed quantitative analyses" are obtained by the use of numerical models, not directly by using initial atmospheric conditions.
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From page 21... ...
Wouldn't one normally expect a data compilation covering 30 more years to have much more data in it? L1993: This error should be cast in terms of errors in some familiar quantity like thermocline depth, and compared to other sources of error.
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From page 22... ...
" Please explain "merged dataset" L2064: What has been (or will be) the tangible benefit of improved reanalysis resolution for climate studies?
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From page 23... ...
L2854: Quadratic cost functions can be constructed without assumptions about the underlying distributions, but interpretation of the results is not so straightforward as it is in the Gaussian case. L2863-4: Straightforward implementations of the Ensemble Kalman Filter cannot incorporate future data; that's why it's called a filter, according to standard terminology in time series analysis.
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From page 24... ...
It would be useful to document studies that have made use of reanalysis data for analyzing climate shifts. The so-called transition around 1976 might be an instructive example.
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From page 25... ...
Spatial variations in summertime surface temperature change are unlikely the result of anthropogenic forcing alone. This chapter is predominantly oriented toward treating drought as an "event", so it fails to discuss the importance of long-term local precipitation trends in altering the rainfall PDF and thereby producing more or fewer drought events of greater or lesser severity.
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From page 26... ...
compared to SST changes occurring simultaneously everywhere (no Rossby wave forcing, but strong anthropogenic influence)
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From page 27... ...
": The committee disagrees with this terminology. The immediate cause of a temperature change pattern is some combination of changes in advection, land surface characteristics, cloud cover, etc.
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From page 28... ...
No, the models are deficient everywhere, and the disagreement in the Southeast US suggests that part of the agreement elsewhere may be fortuitous. L3907-3908: Given what we know about the climate system, it is impossible that any sub-century spatial variations in observed surface temperature change could be due to anthropogenic forcing alone.
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From page 29... ...
Of all the available starting dates for trend assessment, 1951 produces a trend estimate that falls close to the median of the other estimates. L4144: "mid-spread" should be replaced with "wide-spread" L4208: Spell checker Freudian slip.
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From page 30... ...
Change to "…subsequently amplified by local soil moisture conditions, and in some…" L4877: Delete "an" Page 137 – move last bullet to second bullet on page 136. L3094-3103: This text appears to be a discussion of the prediction/predictability question.
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From page 31... ...
This discussion should clearly state that these recommendations will help reduce uncertainties in climate attribution and will develop ways of realizing the benefits of reanalysis data in supporting policy decisions. The introduction of Chapter 4 needs to better explain variability and trends.
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From page 32... ...
This discussion would tie reanalysis and attribution sections together better. R6 states that it is beneficial to go beyond present ad hoc project efforts to a more coordinated and effective national program in climate analysis and reanalysis.
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